PRACTICAL SUBMARINES EXISTED BY 1900, but they were limited to harbours and then to coastal areas. To achieve greater range (and, incidentally, higher surface speed) required reliable, efficient internal-combustion engines, which became available from about 1905 onwards. In 1914 all navies had long-range submarines, but they were only beginning to understand their potential. They could not effectively attack commerce under the universally-accepted Prize Rules, which required that a raider examine a ship and protect its passengers and crew before sinking it. Navies became interested in submarines as elements of, or adjuncts to, fleets. For example, several navies, including the Royal Navy, the German navy and the US Navy, were interested in tactics which would lead an opposing fleet over a submarine trap. Submarines were also the only craft capable of imposing a close blockade on an enemy fleet in the face of his own mines, torpedo boats and submarines. If anything, pre-1914 navies seem to have exaggerated the ease with which submarines could find and attack fast warships in the open ocean.
Submarines were relatively immobile when submerged and whether surfaced or submerged they could not see very far. They had to wait for targets in places they were likely to pass. That meant, for example, the areas immediately to seaward of the entrances and exits of fleet bases and major ports and the focal areas identified many years earlier as likely hunting grounds for commerce raiders. Once in the open sea, a naval force could consider itself reasonably safe from submarine attack, although that was not always the case. Conversely, a submarine was unlikely to encounter targets while transiting from base to a patrol area where it might expect to encounter targets.
Although submarines were equipped during the war with hydrophones, they were not good enough to support an attack conducted entirely on the basis of sound information. A submarine might be difficult to find in the open, but she could not attack without using her periscope. At the very least, a ship sighting a periscope might speed up or turn away; a submerged submarine was quite slow. Torpedo attack created further dangers for the submarine. All First World War torpedoes were propelled by air (in many cases, heated and even turned into steam), which left a visible wake, a warning of imminent attack, but for a fast escort such as a destroyer it was also an arrow pointing back at the firing submarine. Both periscope and array were very fleeting indicators, so there was a premium on quick reaction, particularly to an indicator some distance away. Hence the great interest on the Allied side in depth-charge throwers and various howitzers and charge-throwing guns.
With the ‘D’ class, the Royal Navy began building ‘oversea submarines’ capable of working on the far side of the North Sea, in the teeth of German local defences. This class introduced external (‘saddle’) ballast tanks, which left more volume inside the hull, but also made for poor streamlining. D 1 shows her saddle tanks and also her W/T antennas, with characteristic Royal Navy spreaders to form cylindrical arrays. D 4 of this class had the first British submarine deck gun, a short 12pdr.
Before 1914 increasing torpedo range attracted great naval attention and much affected the tactics of capital ships and of destroyers. However, submarines typically fired single shots from close range. Before the war, British doctrine was to fire from 500 yds and it was presumably typical. Firing was complicated enough that it was difficult or impossible to fire spreads. As the submarine fired, the weight represented by the torpedo was ejected and the air ejecting the torpedo created a visible air bubble. The submarine had to take on balancing water quickly enough to avoid broaching. It was also difficult to shift rapidly from target to target. A submarine might be very effective against one target at a time, but unable to take advantage of a mass of targets suddenly presented, as in a convoy.
To hit a moving target, the shooter has to solve a triangle, the sides of which represent his own speed, the target’s speed and the torpedo’s speed. The solution is to aim the torpedo so that it leads the target just enough to hit. Aim is in terms of the angle between the torpedo course and the target course. The faster (or shorter) the target, the more acute the problem. Unfortunately the submarine could not directly measure either the target speed or its course. Both had to be estimated based on a quick glance through the periscope. The purpose of much First World War naval camouflage was not to hide a ship so much as to prevent a U-boat commander from accurately estimating either key quantity. That applied to dazzle painting and also to false bow waves.
The submarine’s need to show a periscope, perhaps repeatedly, as she prepared to attack explains why it was assumed by both the British and the Germans at the outbreak of war that a destroyer screen would be an effective means of shielding capital ships.1 Given limited underwater speed, a submarine had to get into a position ahead of a fast target. Typically it had to be within ‘limiting lines of approach’ defined by the ratio of torpedo and target speeds (and by submarine submerged speed). To the extent that a destroyer spotting a periscope could run down the submarine, she could keep that submarine out of the attack area ahead of the moving ships. At the outbreak of war the British had thought through a means of destroying submarines occupying the limiting lines of approach. The Germans apparently thought that the presence of destroyers without anti-submarine weapons was enough; Krieg zur See makes it clear that that in 1914 the High Seas Fleet relied heavily on destroyers as anti-submarine ships despite their toothlessness. It might be imagined that a shallowly-submerged submarine which had just exposed its periscope was in danger of being rammed, but lightly-built destroyers had at least as much to fear until they were fitted with reinforced bows.
All submarines of this era were propelled underwater by batteries, which were charged by diesel (sometimes petrol) engines on the surface. Submarines were not designed to run their engines while submerged, although there were attempts to devise means of doing so. For example, some British submariners tried to run while awash with an open hatch, using cloths to keep most water out of the largely-submerged submarine. Submerged endurance was limited, typically less than 24 hours and speed was also very limited. A submarine could make good a substantial distance only when running on her engines, on the surface. She would also run her engines whenever out of sight of potential attackers. It helped that the submarine had a low silhouette which could not be seen at any great distance and that coal-fuelled surface ships generally created smoke which could be seen well over the horizon, either as warning (to dive) or as indication that a target was nearby. The periscope offered a raised vantage point which was not very visible at any distance. Moreover, a submarine had to find its quarry. It could hunt most effectively near a base or a port or in the sort of focal area which had been defined in studies of trade protection. It followed that formations had to be protected mainly either when they emerged from (or returned to) their bases, or when they were near enemy bases on blockade duty.
Any kind of co-ordination between submarines and a central authority depended on W/T, but a small submarine could not initially support a massive transmitter-receiver. The Royal Navy’s preferred solution to long-range control of submarines was to use a surface ship, from which orders could be sent over shorter range to surfaced submarines (in 1914 there was no means of contacting a submerged submarine by W/T, although there were crude underwater sound signals). During the Scarborough Raid, Commodore (S) Roger Keyes was on board the destroyer Firedrake, which was in W/T contact with the Admiralty via Yarmouth. He contacted his surfaced submarines via shorter-range W/T. In this way he tried to control a patrol line he had formed off the Dutch coast, on what he hoped was the escape route of the German battlecruisers (he wanted permission from the Admiralty to move the patrol line). On the other hand, by December 1914 the Royal Navy had submarines positioned off the German coast as pickets more than as attackers and it appears to have received current W/T reports from them.
The Royal Navy
Admiral Fisher was an early advocate of submarines, initially as a means of coast defence. As submarine engines improved, however, he became interested in using them further afield. Submarines were an important element of his ‘flotilla defence’, which initially applied mainly to the British coast and then became an argument that the entire North Sea would probably become untenable for conventional fleets in wartime. He therefore became intensely interested in ‘oversea’ submarines capable of operating off the German coast. The first such craft were the ‘D’ class, followed by the ‘E’ class which was the standard British First World War submarine.
All of this was less purposeful than might be imagined. Initially Vickers developed a series of single-hull submarines from the Holland boats it had built under license (‘A’, ‘B’ and ‘C’ classes). The company, which had an Admiralty monopoly on submarine construction until 1910, determined which improvements it could add in successive classes. Like contemporary foreign submarines, all were powered by petrol engines, whose fuel created poisonous (and intoxicating) vapour liable to explosion. The ‘B’ and ‘C’ classes were the first to be considered ocean-going, but that did not suggest the endurance to cross the North Sea.
The succeeding ‘D’ class (1906–7 programme) was the first DNC submarine design, Vickers developing its details (for a time it was to have been built by Pembroke Royal Dockyard).2 It turned out to be the first overseas submarine, but it is not clear how much that role was taken into account by DNC, hence to what if any extent the ‘D’ class reflected Fisher’s personal evolving vision of future North Sea warfare.3 The design was produced about May 1905 as an alternative to a modified version of the current ‘B’ class, which DNC called C2. Initially the main feature of both designs was increased reserve buoyancy, ‘D’ having saddle tanks and C2 having ballast tanks atop the pressure hull. The object was to improve seakeeping. The French and others had already shown that by moving ballast tanks outside the hull a submarine could gain considerable reserve buoyancy (sea-keeping) and that virtue was unquestioned. The ‘D’ design was chosen over C2 at a 23 June 1905 meeting of the Submarine Design Committee, which included Controller, DNC, Engineer in Chief, Naval Assistant to First Sea Lord (and also former Inspecting Captain of Submarines) Captain Bacon and Inspecting Captain of Submarine Captain Lees. It seems to have been accepted at the outset that this submarine should be considerably larger than earlier ones; C2 was still smaller than French 450-tonners. The Committee opted for the larger submarine with better seakeeping, using saddle tanks. They offered some protection to the pressure hull, which was somewhat better shaped for diving and for steering in a horizontal plane and they made for less hull depth, which meant that the submarine had a lower, hence less visible, silhouette on the surface.4 Both alternative designs invested much of the additional size in greatly increased battery capacity (212 rather than 159 cells) for greater underwater speed and endurance. Armament was doubled, fuel stowage was doubled and both designs featured twin screws. Enlarged hulls provided accommodation for relief personnel, so the submarines could remain longer at sea. There was no discussion of how much longer at sea a submarine had to stay to achieve sufficient performance to operate on an enemy’s coast rather than off the British coast.
Earlier submarines, relegated to coast defence at the outbreak of war, proved useful as a means of attacking U-boats in the waters around Britain. This is C 9. The men standing on the superstructure give some idea of her small size. She also had very limited internal volume due to her single-hull configuration. Four of this class operated in the Baltic. They were scuttled in Helsingfors Bay in April 1918 when the Russian Revolution made further operation impossible.
The ‘E’ class was the wartime workhorse of the Royal Navy submarine service. This is E 20, probably upon completion in August 1915. During the war, British submarines typically had their names painted on their superstructures; pre-war photographs typically show pennant numbers instead. The gun is a 6in howitzer. Note the ship-like ‘plough’ bow (introduced in E 19) for better seakeeping. Initial units had no guns, but experience in the Sea of Marmara (Dardanelles) showed that they were needed. Malta Dockyard installed a 12pdr on board E 11 and a 4in on board E 12. Some North Sea boats were given high-angle 3in or 12pdr guns in 1916–17. Some boats operating in the Sea of Marmara carried spare torpedoes lashed to the casing. ‘E’ class minelayers carried their mines in tubes in the ballast tanks instead of the usual beam torpedo tubes.
Although nearly at the end of the ‘E’ series, E 55 was built by Denny to the original design, its bow poorly adapted to seakeeping. She did not have the topside rudder eliminated after the initial boats in the series.
As with battleships, cruisers and destroyers, in 1914 the Royal Navy took over submarine contracts with foreign navies. E 26 had been ordered from Beardmore for the Turkish navy. These pre-launch photographs show the broad saddle tank of an ‘E’-class submarine but not the unusual beam torpedo tubes (the bow photo shows one of the two bow tubes). The stern view (which shows the cap for the single stern tube) is dated 23 August 1915.
There was some reluctance to accept the increased size and cost in ships which had to be built in large numbers and there was scepticism that simply carrying extra personnel would allow a larger submarine to remain at sea for longer than the usual three days in fine weather and less in bad weather. At the meeting both Bacon and E-in-C (A J Durston) raised the possibility of using a heavier-oil engine. The Royal Navy had been interested in such engines for some time, but as yet no satisfactory engine had been built and tested. Now a diesel was available and it would be tested on board the earlier submarine A 13. It required about 50 per cent more volume than an equivalent petrol engine, but its fuel had only about half the energy content of petrol, hence would make for a slower submarine. Another possibility was a heavy-oil engine that Vickers was developing.5
None of this made the new design an immediate favourite. Third Sea Lord (Admiral Jackson) agreed with other members of the Committee that the navy should continue building the current standard coastal boats (‘B’/‘C’-class) while developing the much more expensive ‘D’ design. DNI (in effect chief of naval staff) Captain Ottley agreed: should the Royal Navy build something which cost as much as a destroyer but had less than half its speed, a third of its radius of action and ‘incomparably worse sea-keeping powers’? That seemed to depend on whether it could be towed at high speed, perhaps by a battle squadron. Fisher agreed to keep building ‘B’-class submarines so as to limit costs.
In November, however, Bacon suggested building a ‘D’-class prototype, presumably reflecting Admiral Fisher’s current wishes. He cited a French newspaper report to the effect that Britain currently led the world in submarines conceived to attack, given their size and general seaworthiness. At this point, to Bacon, ‘overseas’ still apparently meant France. The British lead might soon be lost, as French 1905 and 1906 programmes totalled thirty-six 400-ton submarines, which outclassed the British ‘B’/‘C’ boats. ‘I cannot express too strongly that I feel sure the time has arrived for a further increase in size, speed, radius of action and armament.’ That had been his reason for suggesting the ‘D’ design in the first place. The new (1906–7) Estimates provided for one experimental submarine and he wanted it to be the prototype ‘D’ boat. Inspecting Captain of Submarines Lees agreed, as without the new submarine ‘we shall be left helplessly behind the French’.
It was by no means obvious that the Royal Navy would keep building expensive ‘D’ class submarines. In April and May 1906 Vickers offered three single-hull designs for what it assumed would be the next (‘E) class. All were enlarged versions of the ‘B’/‘C’ class. DNC rejected them; the new ‘D’ design offered too great an advantage, in the form of increased armament, speed, comfort and radius of action. DNC was also interested in trying an alternative to Vickers’ preferred single-hull designs. Apparently the objections voiced so strongly the previous year had gone, but nothing in the surviving Cover shows a shift towards a strategy of forward-deploying submarines. The Committee on Submarine Design formally approved the ‘D’ design on 13 July 1906 and DNC submitted it to the Board on 7 August 1906. That day it received the Board Stamp. By that time 10ft had been added to the submarine’s length and estimated submerged displacement was 580 tons, compared to about 320 tons for the last of the ‘C’ class, The new submarine was powered by a pair of four-cycle six-cylinder diesels. A second large submarine was included in the 1908–9 programme (the gap allowed for completion and trials of D 1) and in July 1909 another six were included in the 1909–10 programme,6 the first in which the earlier coastal type was abandoned.7 As had been predicted, the more expensive ‘D’ could not be built in the same numbers as earlier submarines. The 1910–11 and 1911–12 programmes were six ‘D’-size submarines each; the 1912–13 and 1913–14 programmes were larger, but many of the submarines ordered were experimental.
The ‘L’ class was in effect a stretched ‘E’ without the beam tubes and with a gun on a raised mounting to reflect wartime lessons. The torpedo battery was four 21in bow tubes rather than the four (later five) 18in of an ‘E’. L 2 is shown. Later units had their 4in guns on a raised platform forward of the bridge.
As early as January 1905, much impressed by submarine performance in exercises, Fisher pointed out that a submarine might be used as part of a blockade on an enemy’s coast.8 As with much other new technology, he overrated the ‘D’ class, but a November 1908 memo shows that he clearly understood he now had a new kind of weapon.9 He credited the newest submarine (‘D’ class) with the ability to operate for up to two months at a time, far beyond what any other kind of warship could do.10 Attempts to develop an effective means of ASW had all failed. He concluded that the submarine was the offensive torpedo craft of the future, replacing the destroyer, because unlike a destroyer it could attack equally well by day or night (submarines were already being called ‘day torpedo boats’ because conventional torpedo boats were effective only at night). Given the new capability, it was essential to develop some antidote to submarines equivalent to the destroyer as an antidote to torpedo boats. What Fisher did not write, perhaps because it was obvious to him, was that such an antidote had to be a submarine lying off an enemy’s submarine base, just as the early destroyers were intended to lie off enemy torpedo boat bases, waiting for enemy submarines to emerge and then running them down. Enemy submarines near base would be running on the surface in order to make good any distance to their patrol areas. A British submarine on submerged patrol would have to surface and run them down at maximum speed before submerging to attack. There was no hope, at this point, of attacking a submerged enemy submarine. To some extent Fisher’s paper was prompted by news that, for the first time, the Germans were spending the sort of money on U-boats that the British were already spending on their submarines. A British officer had managed to get aboard the German-built U 3, which was delivered by sea (albeit with escort) from its builders to Pola (Fisher wrote that a British submarine could have made the trip without any escort).
British practice was to aim the submarine at its target and it seemed that the ‘D’ class was the longest which could easily be manoeuvred that way.11 The British rejected angled firing (which was used abroad) on the ground that it required a very accurate range (the torpedo does not turn immediately onto the desired course as it leaves the tube, so the shooter has to take the straight run into account). However, experiments had shown that even without the bar used on board fast ships, a torpedo could be fired from a broadside tube at moderate speed. It turned out that by adding 2½ft to the beam a broadside tube could be incorporated into an enlarged ‘D’ class submarine. The resulting ‘E’ design was 15ft longer than a ‘D’, displacing another 180 tons (it had 24 per cent more reserve buoyancy). The first two submarines of the new type were initially considered the last of the earlier class: D 9 and D 10. They were soon redesignated E 1 and E 2. Six were ordered, plus the Australian AE 1 and AE 2.
The later version of the ‘L’ class was the final development of the oversea submarine series begun with the ‘D’ class in 1908. L 55 is shown, newly completed, in 1919. She was armed with six 21in torpedo tubes and two 4in guns (at either end of her sail).
The pre-war Royal Navy ordered several submarines to foreign designs to gain experience with the double hulls which it hoped would make for higher surface speed. W 2 was based on the French Schneider-Laubeuf design. She was completed in May 1915.
These submarines were clearly considered a stop-gap. British submarine officers considered the saddle-tank ‘E’ class limited. It could not, for example, be driven faster than 15 knots on the surface without the danger of inadvertently diving. That precluded developing it into a fast submarine capable of working with the fleet, an idea already circulating. The fully double-hull French and Italian submarines, with much greater surface buoyancy, could be driven at higher speeds and thus could make use of any considerable advance in engine design. There was also a feeling that Vickers had been too conservative and that foreign designs might be better. DNC produced three new designs in 1911 for the 1911–12 programme: an Improved ‘E’ and two others based on French and Italian practice.12 The Improved ‘E’ was a lengthened version of the existing ‘E’ class design, which officers considered inferior to the two foreign designs.13 DNC was unwilling to order any of the large new designs, as they were too experimental.14
When war broke out, the Royal Navy ordered twenty submarines to the US Navy’s ‘H’ class design. The Vickers ‘H’ class was an improved, lengthened version with 21in rather than 18in torpedo tubes. These submarines proved useful in coastal waters and, after the war, for training. The Second World War ‘U’ class was conceived as a replacement. This is H 28, probably on completion in June 1918.
The point of double-hull design was to provide a submarine with a ship-shaped outer hull for good surface performance. The first major application of this idea was the ‘J’ class, referred to as a ‘Reaper’ in its Ship’s Cover (no explanation is given there). The ‘J’ shared the underwater hull form of the ‘K’ class, but not the power needed for really high speed. The ‘Reaper’ designation suggests that they were intended to ‘reap’ what patrol submarines off the German coast ‘sowed’ in the form of reports of German warships coming out of Wilhelmshaven. J 5 is shown in drydock. The raised and flared bow was introduced because the free-flooding bow initially brought the bow down in a seaway, badly slowing the boats. (Allan C Green via State Library of Victoria)
In September 1910 a new Inspecting Captain, Roger Keyes, replaced Captain S S Hall, who in turn had succeeded Bacon. Hall saw little point in continued improvement, because in his view the key to submarine effectiveness was the commander, the second consideration being reliability.15 It would be best to fasten on a successful design (the ‘E’ class) than to seek higher performance. He did, however, support the 1000-ton enlarged ‘E’ without a bow tube and he commented early in 1911 that a 1000-ton submarine with two good guns would ‘form a most interesting comparison with a destroyer’, which, incidentally, would also fire her torpedoes on her broadside.16 Controller (Jellicoe) was much interested in a ‘submarine destroyer’, which seems to have meant a submarine fast enough to run down any enemy submarine seen leaving port. Keyes rejected further saddle-tank submarines on the ground that they could never evolve into the sort of fast submarine Jellicoe wanted.17
Thus, the Royal Navy still wanted to try something other than the saddle-tank ‘E’ class. Representatives of DNC, E-in-C and Inspecting Captain of Submarines visited both Laurenti in Italy and Schneider in France. They were much impressed by the former and much less by the latter. Both had the desired high surface buoyancy (60 and 40 per cent, respectively), but the French Schneider boats were considered too long, too slow and outdated overall (among other things, they carried some of their torpedoes externally). Under the 1911–12 programme DNC ordered a Laurenti boat from Scotts (S 1) in addition to five repeat ‘E’ class.18 The high surface buoyancy of S 1 influenced later British designs. By the time the British officers had visited Schneider and Laurenti, the US Electric Boat company, which had designed the first British submarines, was also offering a fast submarine, which Keyes described as a compromise between the two European concepts.
After the officers visited Laurenti and Laubeuf, First Lord Winston Churchill ordered a new submarine conference, which met in February 1912.19 It divided future submarines into oversea and coastal types. The oversea submarine was essentially Jellicoe’s submarine destroyer, with high surface speed (20 knots) and high burst underwater speed, to displace about 1000 tons (as in the abortive large ‘E’), with two bow tubes, four beam tubes and one stern tube. Diving time should be no more than three minutes. Later the ‘oversea’ submarine was described as a ship-shaped double-hull craft fast enough to accompany a battle fleet and capable of keeping the sea in all weather (in 1914 that was taken as 20 knots). By 1914 the Germans and the French were thought to be building such submarines, which could more easily achieve high speeds because they did not have to accommodate broadside torpedo tubes. Yet the British considered such tubes essential. The report specifically rejected any development of the ‘E’ class. Successful foreign alternatives were the Laubeuf, Laurenti, Krupp and Electric Boat submarines. It was assumed that diesel engine power could be increased sufficiently to provide the desired speed. A large prototype oversea submarine should be built as soon as possible.
A ‘J’ class submarine operating with the Grand Fleet. (Dr David Stevens, SPC-A)
For pre-war tacticians in many navies, the great goal in submarine development was the fleet submarine, which should be fast enough to work with the battle fleet. The serious problems manifested by the British ‘K’ class have obscured the reality that nearly all the major navies (the Russians may have been the sole exception) were interested in such submarines. All agreed that only steam power offered any hope of achieving the desired speed. In the 1980s a British submarine engineer pointed out that steam was still the only way to achieve high speed – and that the success of nuclear submarines (which have steam plants) proved the point. K 6 is shown as completed.
It was Vickers’ Nautilus, which turned out to be much larger than expected (Vickers also designed the coastal ‘V’ class conceived by the committee). She had even greater surface buoyancy than the Laurenti submarine (800 tons on 1270 tons surfaced) and a complete double hull (Laubeuf type). However, she did not match the desired surface speed; she was limited to 17 knots. She did have the very long surface radius of action of 5300nm. The 1912–13 programme added five repeat ‘E’ class submarines, the coastal prototype V 1 and Armstrong’s W 1 and W 2, which were Laubeuf submarines designed for Greece. The considerable size of the programme – eleven submarines rather than the six of recent years reflected Churchill’s interest in submarines, which was probably due mostly to that of Fisher, his mentor.
The Vickers Nautilus design could not meet the oversea submarine requirement, even though Vickers was thought to have more experience with diesels than any other British firm. For the next year’s programme the Admiralty turned to Laurenti, which guaranteed 18 knots for its Swordfish, but cautioned that it might not make the guaranteed power. Keyes asked the obvious question, which was whether the alternative, a steam turbine, would solve the problem. Scott had already designed a turbine installation which seemed attractive. The Royal Navy was having trouble with the diesels of the ‘D’ and ‘E’ classes and it mistrusted more powerful ones. At the same time it was reported that the Germans had been unable to complete many of their submarines due to engine problems and that the French were reverting to steam turbines in their large submarines. The Swordfish was ordered with a steam turbine, on the theory that if it succeeded, the desired fast submarine could surely be built.
Fisher had argued that submarines would make the North Sea too hot for battle fleets, but many officers, including Fisher’s acolyte Admiral Jellicoe, disagreed. He wrote that, once the submarines had done their best and had probably been sunk, the battle fleets would come out and fight.20 War experience showed that submarines found it difficult to locate cruising fleets, even when they were organised (by the Germans) into patrol lines. The war did create a few choke points at sea, in the form of gaps in minefields and in shallows near the Dogger Bank, but for the most part warships were endangered only near their bases, where submarines could wait for them.
Navies, including the Royal Navy, became interested in how a submarine working with a fleet could be used during or immediately after a fleet action. Both the Royal Navy and the German navy experimented with ‘submarine traps’ during their last pre-war exercises, the idea being to deploy submarines in advance so that the enemy fleet could be led over them. Given a limited submarine force, the idea implied that the submarines in question should be fast enough to work with the fleet.
On this basis, some time in 1913 a third type was added: the ‘ocean’ submarine which would work with a fleet. First Lord Winston Churchill defined it in a 20 August 1913 memo, although the idea probably came earlier: ‘the Ocean Submarine is a decisive weapon of battle and as such must count in partial substitution of battleship strength’.21 In Churchill’s memo, the ‘ocean’ submarine had 24-knot speed. The idea of substitution was significant: when he wrote his memo Churchill was having real problems selling his 1914–15 programme. The governing Liberals expected to fight an election in 1915 and they badly wanted to do so on the basis that they had increased social spending without increasing taxes. It seemed likely that the single largest item of defence spending, the naval budget, would be cut. Churchill was looking for ways out, including persuading the Canadians to pay for new battleships. In fact the large 1914–15 budget was approved with its four battleships, but by that time Churchill was interested in buying submarines and other torpedo craft rather than battleships. He continued to explore such options in the spring of 1914. In 1913, then, DNC designed a large ‘ocean’ submarine. It was deferred while Nautilus and Swordfish were built. Nautilus was seen as a prototype very large submarine and Swordfish as test submarine for a British steam plant.
High speed meant high surface speed and a low bow made for poor seakeeping. K 3 is shown off Scapa Flow on 4 December 1917 at 20 knots in Sea State 3. This class introduced a fully-enclosed bridge structure, which provided protection against this sort of sea. Note the high masts for good W/T performance.
It did not help that these submarines were given a powerful gun armament on deck. K 3 shows her two 4in guns and one 3in high-angle gun (closest to the bridge); note how much spray she threw up even in a moderate sea.
Aside from the two experimental submarines, the only oversea submarines in the 1913–14 programme were two repeat ‘E’ class. They and the ‘Ds’ were Keyes’ only submarines capable of oversea patrols, the ‘E’ class much preferable to the ‘D’ (which should be relegated to coastal work as soon as possible).22 At this point Keyes’ possible oversea submarine roles were (i) blockade and (ii) work with a battle or cruiser squadron.23 Everything else in the 1913–14 programme was the new coastal type, albeit somewhat larger than expected: Scotts’ S 2 and S 3; Vickers’ V 2, V 3 and V 4; and Armstrong’s W 3 and W 4. The Vickers monopoly having expired, a DNC-designed coastal submarine (F 1) was ordered from Chatham.
The British programme was discussed at a conference in First Lord’s room on 9 December 1913.24 British policy was to revive the previously projected close blockade of the German fleet, but this time by submarines which could survive in waters near the German coast.25 This idea had been discussed for some time. The rub was insufficient numbers; eventually a goal of four flotillas, each of twelve overseas submarines, was set.26 The standing requirement for coastal submarines was reaffirmed, but as yet there was no agreed number of coastal submarines.
The conference discussed DNC’s design for Churchill’s 24-knot ‘ocean’ submarine.27 DNC showed great confidence in the design and commented that even if it failed as a submarine it would be a formidable surface torpedo ship like the old torpedo ram Polyphemus (Churchill would soon become interested in a new Polyphemus-like ship). Churchill repeated his earlier view that, scouted for by fast cruisers, such a submarine could overtake and work around an enemy surface force. That was much the way post-First World War navies such as the Imperial Japanese Navy planned to use their big cruiser submarines. Keyes saw no insurmountable problem, but he pointed out just how great a leap the new submarine would be. It would displace three times as much as an ‘E’ and would be nearly twice as long, which would complicate diving control. Its much greater reserve buoyancy would require it to take on far more water when diving. Its steam plant would have to be shut down and cooled and it would produce three times the power of the experimental Swordfish. The Nautilus would provide experience in handling so large a submarine and the Swordfish would show how her steam plant should be operated. Churchill did not want to delay building repeat ships until the first had been tested, but Keyes extracted an agreement not to proceed until Nautilus had been tested. A second Swordfish, but not a repeat Nautilus, was therefore included in the 1914–15 programme.
The cure for the wet bow was a big ‘swan bow’, shown on K 16 in a post-war photo. The gun battery was relocated to the raised deck abaft the bridge. A new open bridge was built atop the earlier enclosed one to clear the line of sight over the raised bow.
By the end of the war, submarines were being armed with depth charges so that they could react quickly to diving U-boats. K 22 sported a depth-charge mortar at the after end of her gun deck, with her 3in high-angle gun between her stacks. Her forward stack is tilted in preparation for diving. The gun between it and the bridge is her 4in.
Keyes still much preferred double-hull to saddle-hull submarines. He was attracted by a Vickers proposal for what amounted to a double-hull ‘E’ class submarine, the ‘G’ class. Compared to an ‘E’ class submarine, it cost considerably more but offered somewhat higher speed (given in 1913 as 15.5 knots rather than 13.5 knots) and more torpedo tubes (one bow tube, two broadside tubes and two stern tubes rather than one bow, two broadside and one stern tube; and the bow tube in the new design was 21in rather than 18in).28
At the end of the December 1913 conference, one double-hulled ‘E’ class submarine replaced one of the planned coastals, so that the 1914–15 submarine programme stood at two Vickers double-hull ‘E’ class, one Dockyard-built double-hull ‘E’, seven coastals and the repeat Swordfish. Not long after the conference, Second Sea Lord (Admiral Jellicoe) wrote to Churchill that the programme made him uneasy. He had understood that the programme of coastal submarines could not be changed, but he feared that the coastals were being bought in quantity because of a false impression that they could somehow be used for oversea work. Third Sea Lord agreed with him. Churchill reviewed the situation a few days later and decided to recast the 1914–15 programme. He would eliminate the repeat Swordfish and buy the maximum number of double-hull ‘Es’ as he could without breaching contracts.29 That was not too difficult legally because five of the coastal submarines were being built by Chatham Royal Dockyard, which was not constrained by any commercial contract. Chatham received the orders for the five oversea submarines in June 1914. Thus the final programme consisted of seven of a new Admiralty Improved ‘E’ (‘G’) class and, despite the conclusions drawn in December 1913, two more coastal submarines (F 2 and F 3).30
Churchill also considered adding more submarines in place of one of the four battleships of the 1914–15 programme.31 In May 1914 he apparently told Fisher that First Sea Lord Battenberg approved the idea, but that Jellicoe (already Grand Fleet C-in-C designate disagreed strongly.32 Fisher accepted Jellicoe’s arguments that any such plan would destroy the attempt to convince the Canadians to provide battleships (an ultimately-doomed plan, but that was not yet obvious), it would shatter the battleship standard that the Royal Navy used to justify its building programme and it might fail because it would be difficult to get the submarines in the first place. He wrote, however, that he believed (wrongly) that Tirpitz was now surreptitiously increasing German submarine strength, so at any cost the British must accelerate their own programme. In July, Churchill sent First Sea Lord Battenberg a proposed revised 1914–15 programme in which fifteen submarines were substituted for one of the battleships.33
The expanded 1914–15 programme was a problem, because Vickers was still the main submarine builder. It was also already failing to meet delivery schedules. Chatham had never built a large submarine and further capacity would take time to come on stream. Vickers was also an export builder and in the wake of the Balkan Wars both Greece and Turkey were anxious to buy ships, including submarines. In February 1914 it seemed likely that Greece would try to buy four to six ‘E’ class submarines (in fact it was Turkey which ordered two).34 Vickers apparently received a Greek order, but it was cancelled.35
By November 1914, many of the submarines under construction were badly delayed.36 Among the first tasks put to newly-returned First Sea Lord Admiral Fisher was to accelerate submarine production. Churchill asked for twenty more submarines. Fisher did much more: he created a massive new programme. He ordered twenty small coastal submarines from Bethlehem Steel in the United States (‘H’ class). They were not what the Royal Navy wanted, but they were more or less immediately available (although in fact diplomatic problems connected with American neutrality slowed delivery).
Most of the programme was inevitably repeat ‘E’ class submarines, because the iron rule of such mobilisation is to keep building what is already being built.37 Investigation showed that an ‘E’-class submarine could be built faster than a ‘G, so new orders were for ‘Es’ (an order for eight ‘G’ class submarines had been approved in September, but not placed, probably due to congestion in the yards). Fisher created his large a programme by bringing in many more builders. Aside from the H class, the programme consisted entirely of medium-speed oversea submarines: G 8–G 15 (G 15 was cancelled 20 April 1915) and E 19 to E 56, of which E 27 and E 28 were cancelled but work on E 27 was resumed in 1915. Six submarines were completed as minelayers (E 24, E 34, E 41, E 45, E 46 and E 51).
Interest in the big ‘ocean’ submarine survived. Of the two test submarines, Nautilus was launched in December 1914 but not accepted until October 1917. Presumably she demonstrated that a long submarine was controllable. She also introduced a new 1850bhp 12-cylinder Vickers engine; the engine of the ‘E’ class developed only 850bhp. She was never fully operational. Swordfish was launched in March 1916 and completed in July. In theory she tested a prototype steam plant, but by the time she was complete the decision had already been made to build the 24-knot steam submarine. However, in designing the steam plant for this submarine Scotts met and solved many of the problems inherent in the larger and more powerful (10,000shp vs 4,000shp) 24-knot submarine. They included developing central control capable of shutting down the many openings a steam submarine required, so that she could dive reasonably quickly. Having proven the underwater steam concept and not being any faster than a conventional diesel submarine, Swordfish was converted into a surface patrol vessel less than a year after completion.
Late in 1914, then, the ‘ocean’ design was in hand but the two prototypes considered necessary to test its features had not been completed. Late in 1914 it was reported (incorrectly) that the Germans had some 22-knot submarines in service.38 Fisher decided to build some fast submarines, in effect the ‘submarine destroyers’ of earlier interest. At this point the steam plant was not yet ready, so the only option was diesel power. The big new engine planned for Nautilus also not yet having been proven, Vickers offered to expand the eight-cylinder engine of the ‘E’ class to twelve, for about 1200bhp. To further increase power, a third propeller shaft was provided. The submarine was designed around its engines, a particularly efficient hull form being chosen. All of these compromises precluded reaching 22 knots, but a speed of 19.5 to 20 knots was quoted (which actually considerably exceeded German performance) and in practice this submarine could reach 19.5 knots. Six were ordered for the Royal Navy in January 1915, followed by a seventh specifically for the RAN (J 7).
Jellicoe badly wanted submarines to support the Grand Fleet during a fleet action. He was well aware of the pre-war 24-knot fleet submarine and he seems to have been the reason the ‘K’ class was built.39 The dates of the drawings suggest that he made his request about March 1915. The existing Admiralty design was chosen over an alternative offered by Vickers.40 As a cover, ships were referred to as flotilla leaders and later as ‘K Class Flotilla Leaders’.41 The first two (K 3 and K 4) were ordered from Vickers in June 1915, followed by others up to K 14 in August. Three more were ordered in February 1916. K 3 made 23.84 knots on trial despite being at greater than designed displacement, due to some flooded tanks. The ‘Ks’ were much longer than previous British submarines and it seems unfortunate that no experience was gained with the big Nautilus before they were built. Given great length and very little reserve buoyancy in the bow, they could easily dive steeply, so that parts of the hull could quickly get below the designed diving depth of 200ft. The original low bow also made for poor performance in a seaway. One was lost when not all of the openings were closed as intended. The main problem of the ‘K’ class, however, was tactical. Despite intense interest in using submarines as part of the fleet, little had been done to ensure that the fast ‘K’ class did not become entangled with surface units, which would always tend to shoot first and ask questions later when confronted with unknown submarines. Both during the First World War and later, the ability to distinguish friendly from enemy submarines was notoriously poor. That, more than anything else, made the sort of fleet support operations widely discussed pre-war impossible.42 The great demonstration of the problem was the ‘battle of May Island’, when two were sunk by collision, one with another ‘K’-class submarine.43
The Royal Navy explored submarines’ potential to a greater extent than any other. Its ‘M’ class were submarine ‘monitors’, but their 12in guns were really an alternative to torpedo tubes in an era of relatively unreliable torpedoes. This photograph was taken soon after the war.
Diesels offered submarines, or at least U-boats, endurance unimagined before the war. As an indication of the sort of effective endurance with which U-boats were credited in 1914, when Scapa Flow was found unsafe due to a lack of submarine obstructions, the Grand Fleet was temporarily based on the West Coast of Scotland and on the Northern Irish coast, which were considered beyond U-boat range. Visiting Newport, Rhode Island on 7 October 1916, U 53 demonstrated much greater range. Note the US cruiser in the background. Her rated endurance was 9000nm at 8 knots, compared to 7600nm for the last pre-war class (U 19). She was a Mobilisation type U-boat with four torpedo tubes, two forward and two aft and a vertical stem rather than the sharply raked one adopted later. Commissioned on 22 April 1916, she survived the war.
The main ocean-going German submarine was the ‘Mobilisation’ type. U 111, launched in September 1917, was turned over to the US Navy. She is shown at the Philadelphia Navy Yard on 6 April 1920. This dry dock view shows the double-hull (ship-shaped outer hull) design adopted by the Germans. Note the heavy gun battery: one 10.5cm/45 and one 8.8cm/30 aft. The torpedo battery was four tubes forward and two aft. Note the sharply raked bow, for open-ocean seagoing, which contrasts with the vertical bow of U 53.
From a more technical point of view, the ‘Ks’ did what was expected of them: they could and did keep up with the fleet. In September 1918 two of them actually overtook the Grand Fleet, but at that time it was hove-to in a gale.44 To achieve the high desired speed the designers had to use a very long, inherently unmanoeuvrable, hull and the low freeboard of the ‘K’ class (otherwise an important submarine virtue, since it helped the submarine evade detection even when surfaced) made it difficult for friendly surface ships to see. For its part the Royal Navy continued to see the virtue of submarines which could co-operate tactically with a surface force, as indeed did other navies. The Royal Navy continued to operate the improved K 26 until she was discarded in 1931 due to the limits imposed by the 1930 London Naval Treaty on total submarine tonnage. As an indication of contemporary views, the US Navy showed considerable interest in fleet-speed steam submarines in 1917–20.
Having asked for submarines which could keep up with the Grand Fleet, on 24 July 1915 Jellicoe asked that a flotilla of the existing slower submarines be provided. He knew that they could not keep up with his fleet, but he already planned to rendezvous at sea with the Harwich Force and he could do the same with submarines based in the Tyne. Pending supply of fast enough submarines, he would make do with groups of three ‘E’ or similar type, with one destroyer to escort each three. The Admiralty told Jellicoe that submarines were in too short supply, but that his request would be reconsidered when more were in service.45 Jellicoe visited the Admiralty to press his case and in November he was rewarded with twelve ‘E’ and ‘G’ class submarines of the 11th Flotilla, to be based at Blyth. He was also promised ‘J’ and ‘K’ class submarines when they became available. In November he was told that, since the ‘E’ class submarines were too slow, he would be getting ‘Js’ and ‘Ks’ when they became available. Grand Fleet Battle Orders were revised to include supporting submarines. Each Grand Fleet submarine was to be given one of the new long-range torpedoes because it seemed likely that a submarine operating with the cruiser (scouting) line or in a flank position might be able to make a ‘browning’ shot before getting into range to fire the usual close-range submarine torpedoes.46
Submarine co-operation with the fleet required long-range W/T, meaning the powerful Poulsen set. As of February 1916 the Grand Fleet had none, but it was decided that the ‘Js’ and ‘Ks’, which would all be assigned to the fleet, should have the new sets. As soon as the six ‘Js’ and the four Talisman class destroyers assigned to work with them had been fitted, the fleet flagship Iron Duke and the flagships of the dreadnought battle squadrons and then of the Battlecruiser Fleet and the 2nd Cruiser Squadron (his scouts) would be fitted, in that order. Poulsen equipment was particularly wanted because in the past submarines off the Norwegian coast had been unable to receive even the highest-power signals from Scapa. Ultimately the Admiralty approved a high-power shore set instead of one on board a fleet unit, presumably because it would be less likely to give away the position of the fleet.47
The bridge of U 111, photographed at Philadelphia Navy Yard on 8 April 1920. US officers who crossed the Atlantic aboard the surrendered U-boats were surprised at how dry they were and at how well their diesels ran.
U 117 was a cruiser minelayer surrendered to the US Navy. Unlike the small UC-boats, she had dry mine stowage in the form of tubes with conveyer belts to carry the mines aft to be dropped. This is her mine stowage.
Given the experience of a year of war, a Submarine Development Committee met in 1915.48 To the existing three types (including the new fleet submarine) it proposed to add three more: a cruiser submarine, a minelayer and a monitor. The cruiser was a long-range submarine with a heavy gun armament (two 5.5in), conceived as a stretched version of the ‘E’ class powered by the new engines of the ‘J’ class. It became the ‘L’ class. The minelayer would be an adapted ‘E’ class submarine. The idea of the monitor seems to have been that existing torpedoes were not proving reliable enough. A heavy shell could travel further and more accurately – and reliably. Three repeat ‘K’ class submarines (K 18, K 19 and K 20) were reordered as monitors (‘M’ class) and a fourth added. All were renamed in a new ‘M’ series on 25 June 1918.49
Of the submarine committee’s projects, only the cruiser submarine produced much. The first two ‘L’ class submarines were ordered as E 57 and E 58, then redesignated because this was different enough to be considered a new class. After the series of ‘K’ class orders in August 1915, the next series of submarine orders came in February 1916: four ‘K’ class (one, K 18, soon reordered as a monitor) and the two stretched and otherwise modified ‘E’ class. Seven more submarines were ordered in May (a second monitor and L 3–L 8) and three more in August (two monitors and L 9). By this time production of ‘E’ class submarines was nearly complete, so some industrial capacity was available.
In October 1916 the Admiralty wrote to Jellicoe that a ‘very substantial’ new programme of submarine construction was imminent, although he should be aware that no such programme could begin without interfering with the construction of surface ships which were also urgently needed. It was hoped that about twenty-five more submarines of the ‘E’, ‘G’ and ‘K’ classes would become available on 1 April 1917.50 The letter to Jellicoe reflects orders for twenty-five L class submarines in December 1916: L 10–L 35. L 50–L 55 were ordered in January/February 1917 and L 56–L 74 (nearly all later cancelled) in April 1917.51 There were also repeat orders for the much smaller ‘H’ class.
The ‘L’ class of 1916 was not the 1000-ton super-’E’ class offered in 1912. It had four bow tubes (double the bow armament of an E) and more powerful engines. From L 9 on, the bow tubes were 21in and minelayers omitted beam tubes. An ‘L’ was about 50ft longer than an E with a pressure hull of 7in greater diameter, with a new stern form (chisel-shaped, as in an ‘H’). Submarines with 21in tubes gained another 7ft 6in in length. The L 50 class was further modified to increase bow firepower to six 21in tubes (there were no longer any broadside tubes), as in post-war submarines.52
By the end of 1916 the British considered a German submarine offensive imminent. Submarines and mines were their most effective ASW weapons. Beatty complained in January 1917 that of eighty-six submarines in British waters on 28 December 1916, only ten were in forward positions where they could sink U-boats: one on patrol off the Maas, five off Terschelling in the North Sea and four patrolling off Horns Reef and the Skaggerak. The rest were reserved for defence of the British Isles (and also for support of the Grand Fleet). Beatty called for total reorganisation, which would provide at least forty submarines for offensive action.53 The catch was that under winter conditions a submarine might well fail to spot a U-boat until it was very close. Beatty’s submarine commander wrote in January 1917 that although submarines were not primarily intended to fight each other, but ‘if surface targets are not available, the submarine can be employed to advantage on this service. Under favourable conditions a submarine can deliberately attack and destroy an enemy submarine which is unaware of its presence. This is a man to man fight as both submarines start on the surface and the one that observes the other first has all the advantage . . . our submarine officers have had more experience than the Germans and should come off well’. He did not think that submarines on this service should do so submerged. At this point oversea submarines (now called patrol submarines and including the small ‘H’ and ‘V’ class units) were mainly being used to watch the Heligoland Bight for German warships going to sea or returning. In addition to watching German waters for U-boats, the substantial force of coastal submarines retained in Home waters on anti-invasion duty could deal with U-boats in their own hunting areas. Some of the proposed coastal ASW patrols were soon begun.
The success of ‘merchant U-boats’ demonstrated to the Germans that they could build submarines capable of sustained operation on the far side of the Atlantic. U 151 is shown at Cherbourg in 1920 alongside the old French steam submarines Thermidor and Fructidor (note their single stacks and the 75mm gun visible on board one of them). U 151 was to have been named Oldenburg as a commercial submarine, but was completed in July 1917 as a U-cruiser. Her broad (unhydrodynamic) hull is evidence of her merchant ship origin. Rated range was 25,000nm at 5.5 knots. (Robert W Neeser via US Navy Historical and Heritage Command)
Under these circumstances it was natural to design a specialised ASW submarine, the ‘R’ class.54 These submarines were to lie in ambush. If the U-boat came towards the ‘R’-boat, she could fire a heavy torpedo salvo. She was also given a high submerged speed so that she could close with a target seen at a distance. Since she could not catch up with a U-boat seen going away, the design incorporated a 4in gun for surface fire (later ‘L’ class submarines had two 4in guns for much the same reason). It does not appear that any ‘R’ class submarine had a 4in gun as completed. DNC’s March 1917 proposal was rejected, but later in the year Commodore (S) suggested that the design be completed and it was approved by the Board later in 1917. Twelve were approved at a 2 October 1917 Admiralty conference (ordered in December), of which two were cancelled on 28 August 1919.55 The initial design called for four 18in bow tubes and a submerged speed of 13.5–14 knots (11–12 knots on the surface) using ‘H’ class machinery. As built they had six bow tubes, a submerged speed of 15 knots and a surface speed of 9.5–10 knots with one rather than two ‘H’-class diesels. They were slightly smaller than the later ‘H’ class (410 tons vs 438 tons surfaced). Unlike the patrol or oversea submarines they reverted to the single-hull design of the earliest British submarines. The most striking feature was the sensitive combination of five hydrophones, which it was claimed made it possible to approach an enemy to firing position without using the periscope.56
Compared to German submarines, at the end of the war the British considered theirs better, with one essential exception: engines. In 1914 the British hoped to test alternative engines in their ‘G’ class, but once war began they had to standardise on the Vickers diesels of the ‘E’ class. The only important wartime development was to add cylinders so as to gain more power. The ‘E’-class diesel itself was an eight-cylinder version of the six-cylinder engine, the first British naval diesel, in the ‘D’ class. The larger engine in the ‘J’, ‘K’, ‘L’ and ‘M’ classes was a twelve-cylinder version of the same engine. It was reliable enough for wartime service, but it paled in comparison with the four-stroke MAN engines used by the Germans. A German engine delivered three times the power in the same weight and it required far less maintenance. The US Navy, which came to admire the British submarines alongside which its own served, copied the German engine after the war. US submarine designer E S Land, later Chief of the Bureau of Construction and Repair and then chief of the Maritime Administration, said immediately after the war that ‘boat for boat I consider the L 50 class of the British design to be the equal if not the superior of the U-boat. If the engines of the two were traded, the British boat would completely outclass the German boat. The British boats are better designs so far as the design of submarines is concerned.’57
The German Navy58
Tirpitz famously had little time for submarines. He said that he did not want to finance experiments, but it also seems fair to say that he was interested in a visible fleet and no matter how effective, submarines did not contribute to the prestige value of the Imperial Navy. Tirpitz also had no use for coast defence, because his entire programme was intended to move his navy away from small coast-defence ships towards large blue-water capital ships. Thus, unlike the Royal Navy, he also had no interest in coastal submarines. In 1914 his U-boats were by far the longest-legged German warships, but not so much because they were intended for long-distance service; it was just that diesels were so efficient. As a consequence, the Germans were able to deploy U-boats to the Mediterranean in 1915, with real impact on the Gallipoli campaign. The same U-boats were most prominently used in the submarine war against British and Allied trade.
By the end of the war, the Germans were placing very powerful guns on board U-boats. In 1918 U 155 was rearmed with two 15cm/40 guns from the old battleship Zähringen, one of which is shown. To meet such powerful weapons, the British planned to introduce a 5.5in gun specifically to arm merchant ships. The war ended before it entered production. She was on display in London after being surrendered on 24 November 1918. U 155 was unusual in that initially she had only external torpedo tubes, which could not be reloaded while she was submerged.
Initially, like surface torpedo boats, German submarines were managed by the Torpedo Inspectorate (TI), but in December 1913 a separate U-Boat Inspectorate (UI) was created. It was responsible for U-boat design and training and for operational doctrine. As the branch with technical expertise, the UI (and the TI before it) set characteristics and evaluated designs. It developed designs for submarines built by the Imperial navy yards, initially the Danzig yard. However, in the fractured German system, the UI could not control U-boat operations. It was up to the Navy Office (which, until 1916, meant Tirpitz) to decide whether and how many U-boats to build in any given year. Moreover, the Navy Law system encouraged a rigid long-term approach to both funding and numbers, despite the contradiction between the two as ships developed. The absolute priority Tirpitz assigned to capital ships presumably drastically limited spending on subsidiary types such as submarines; U-boats benefitted in that they were so inexpensive that their construction did not seriously impact that of the larger ships.
The contradiction between technological development and rigid funding shows in the 1912–14 programmes. There was enough money in 1912 to order eleven U-boats (U 31–41) from a single builder, Krupp. That was the first year of a new Navy Law extending through 1917. Presumably it seemed wise to front-load U-boat construction when capital ship costs were escalating. The consequence was much smaller projected programmes for successive years. The habit of long-range planning shows both in pre-war and in early wartime thinking. The goal of seventy U-boats proposed in 1912 was to have been met in 1919, the end year for the 1912 Navy Law. When the UI proposed a large programme in 1915, it looked toward completion about 1924. It is not clear whether anyone involved realised how absurd that was. Some conversations between Tirpitz and other high command officers in 1914–15 indicated a belief that the war begun in 1914 would end in a compromise peace, after which Germany would fight a greater war against England for what Tirpitz always called ‘world power’. Until at least October 1918 the view at the top seems to have been that the war would end in some sort of armistice, to be resumed later and that U-boats would then be an effective offensive arm, or at the least a deterrent to hold back Allied peace demands.
German policy for the use of U-boats varied considerably after 1914. However, submarines could not be built very rapidly; the record for full-size submarines, set in 1915–16, was eleven months. There was an initial burst of construction orders upon mobilisation in August 1914, but given the assumption that the war would be short, nothing followed until February 1915. By that time it was generally accepted that the war would last at least past the autumn. The Germans had announced unrestricted submarine warfare, but they knew that they had nothing like the force required to execute it. There had been little or no planning for such a campaign during the autumn of 1914 and no effort to design U-boats which could be built more quickly in larger numbers. Nor had there been any equivalent to Fisher’s dramatic expansion of the British submarine-building base. Probably the worst problem was diesels; MAN could produce no more than a pair (for one U-boat) per month. Expanding production meant adding many diesel producers, some of which must have been considerably better than others.
Given the inherent constraints of construction, the U-boats ordered in the spring of 1915 became available in the spring of 1916, just as the Germans found themselves pulling back from unrestricted submarine warfare under largely US pressure. Under those circumstances the most effective way for U-boats to attack British shipping was to lay mines, but when programmes were framed in 1915 torpedo or gun attack was more effective than minelaying. When the U-boats were ordered to adhere to the Prize Rules (stopping and examining merchant ships and placing passengers and crew in boats before sinking them), the UI tried to design armoured and heavily-gunned U-cruisers, the construction of which would have interfered with that of more conventional U-boats.
Also, until well into 1917 U-boats were by no means the highest German naval priority. Much more of the effort went to capital ships, both the remaining battleships and battlecruisers of the pre-war programme and no fewer than seven battlecruisers ordered automatically to replace large cruisers and battlecruisers lost during the war. The UI was only one hungry mouth among many demanding new ships. When it finally did receive priority in 1917, it was far too late, because the first fruits of the new programme were not at sea until 1918, when the anti-shipping war was being lost due to convoy operations and also to improved means of hunting U-boats. The Germans still thought that they could win the U-boat war; as in 1945, morale remained high. It is not clear whether the increased numbers (but not new technology) which would have been available in 1919 would have won. By that time new Allied programmes would also have been far more effective, given massive US destroyer and merchant shipbuilding and a considerable expansion of air ASW.
U-boats were designed both by Germania (Krupp’s shipbuilding arm) and by the Imperial Navy (as supervised by the UI). Pre-war relations between Krupp Germania and the TI were complicated by Krupp’s willingness to export submarines. German policy in general was to prevent export of designs the navy was using, so that when MAN began to make four-cycle diesels for the German navy it generally exported far less reliable two-cycle ones (as the pre-war US Navy learned to its cost).
After the success of the Forelle, a Krupp boat built for Russia, Tirpitz approved two submarines in 1904: the Krupp (Germania)-built U 1 and the navy-designed and built U 2 (Project 7). U 1 was based on Krupp’s design for the export Karp class for Russia. Both Germania and the official designers developed alternative designs from then on.59 Unlike contemporary foreign submarines, both U 1 and U 2 were powered by engines burning paraffin (kerosene) rather than petrol.60 In 1907 the TI turned down a Krupp design for an enlarged U 1 because the company was selling two ships of this type to Austria-Hungary, the only close German ally. Norway bought a similar submarine as Kobben. It did not help that Krupp’s submarine designer, d’Equivilley, was a foreigner (in 1907 he was replaced by Hans Techel, a German). Soon after d’Equivilley left Krupp received its second contract, for U 5–U 8 (U 3 and U 4 were built by the German navy at its Danzig yard). These were Germania-designed substantial twin-screw submarines with two bow and two stern tubes. They had gyro-compasses, an important feature in a boat filled with metal which precluded the use of a magnetic compass. The German navy built four similar submarines (U 9–U 12) and these eight 500-ton U-boats were the first true seagoing U-boats. Aside from relative inefficiency, paraffin created very visible white smoke. The pre-war German navy found that a much more expensive form of paraffin minimised the smoke and reserves were earmarked for wartime use only.
Specially-designed U-cruisers like U 140, shown after surrender to the US Navy, were considerably more efficient (and much faster) than the ex-merchant U-boats. Rated surface speed was 15 knots and endurance was 17,750nm at 8 knots. The guns were two 15cm/45.
The bridge of U 140, with an Eagle Boat in the background.
In 1910 the navy ran exercises in which several of the new U-boats tried to operate together, the TI later stating that unless some form of effective underwater communication was developed, such operations were too dangerous. The accounts in Krieg zur See show in some detail how boats were allocated separate patrol areas, although given the limits of navigation at the time it is difficult to see how this practice could have succeeded, as sometimes the sectors were quite narrow. The official history also gives examples of submarines which completely lost their bearings so that they barely recognised where they were near the British coast.
As in the Royal Navy, the most important pre-war machinery development was the adoption of diesel power. Krupp had installed diesels in the Russian Karp even before the Körting engine was ordered. The leading builder, which became the supplier to the German navy, was MAN (Maschinenfabrik Augsbert-Nürnberg). Its initial proposals were rejected first as too heavy and also because of long delivery time. In 1907 MAN offered a 300bhp six-cylinder engine (note that at this time Vickers was offering 600bhp in the six-cylinder engine for the ‘D’ class). A prototype was ordered in 1908. Germania began building its own diesels in 1906 and, as in the United Kingdom, there was interest in the Italian FIAT engine. In 1908 the TI asked for proposals for an 850bhp engine (450 rpm). The last Körting engines, in U 17–U 18, developed 350bhp each.61 U 17 seems to have been a turning point, since her rated endurance was far greater than that of her predecessors: 6700nm at 8 knots rather than 2100nm at 15 knots. The two figures are probably equivalent (displacement and power did not change), but the much greater figure given for U 17 suggests long- rather than short-range operations. This submarine was designed soon after the first tactical trials were completed in 1910–11.
The TI had hoped for some time to shift to diesel power in a larger submarine, but it would not do so until a powerful yet light enough diesel had run for six days without interruption. MAN produced the first test engine in August 1910, after two years of development of a four-stroke engine. Germania experienced problems with its two-stroke engine, but ran a successful test in June 1911; the engine was installed in the submarine Atropo for Italy. Other engines ordered from FIAT, MAN (Nuremberg) and Körting all failed. MAN’s four-stroke engine was quieter than Germania’s two-stroke type and used less fuel (190g/BHP/hr vs 220g/BHP/hr), but it suffered more from torsional stress in its crankshaft, which was understood to be a serious problem (the solution was generally to add heavy weights to move the resonant frequency away from that produced by the engine). The first diesel U-boats were U 19–U 22, assigned to the navy yard at Danzig, powered by MAN engines. In effect U 19 was the prototype of pre-war U-boats, displacing 650 tons with an endurance of 7600nm at 8 knots. Germania received a contract for U 23–U 26, to be powered by its two-stroke engine; another four MAN-powered boats were ordered from Danzig (U 27–U 30). It turned out that the decision to buy the Germania diesels had been premature. From here on MAN four-stroke engines were dominant, but Germania engines continued to be bought.62 The 1912 programme included another eleven Germania boats, U 31–U 41. As with the battle fleet, the Navy Laws provided only limited financing. In June 1912 plans were announced for further U-boat construction: three in 1913, three in 1914, four in 1915, five in 1916 and six each year between 1917 and 1919, with experimental boats (FIAT engine and caustic-soda closed-cycle propulsion) planned for 1920.
In 1912 UI proposed a deployment (and force growth) plan combining a defensive line around the Heligoland Bight and offensive operations in the North Sea. It required a total of seventy U-boats, which were to be completed by 1919.63 When war broke out U 31 class submarines were being launched (the last was U 41, launched on 10 October 1914). These submarines were armed with two bow and two stern torpedo tubes and they typically carried six torpedoes (later 9–10 torpedoes in some). The last pre-war orders were for U 43–U 45 (Project 25).64 The navy’s mobilisation plan called for 17 duplicates of the latest (U 41 [Krupp] and U 43) design, of which U 46–U 50 were ordered from the navy yard at Danzig on 7 August. The remaining twelve were called the Mobilisation (Ms) type. Germania got the next six (U 51–U 56) and after protracted negotiation Weser, which had been experimenting with caustic-soda steam propulsion, received a contract for U 57–U 62, which duplicated the much earlier U 27.65 These were all twin-screw submarines and diesels (one per shaft) were probably the production bottleneck. The U-boats were all assigned to the High Seas Fleet and they were based with it at Wilhelmshaven on the North Sea. Like the British, the Germans saw submarines as a valuable adjunct to a battle fleet. Co-operation with the surface fleet was first demonstrated in the German 1913 exercises and U-boat capability impressed the fleet command.
Soon after the outbreak of war UI was asked for a design of a small submarine which could be in service before the expected short war ended.66 By late 1914 two classes of such submarines were being ordered, mainly for use from the new German base in Flanders. From there they could easily reach British coastal waters. The UB design was chosen in September 1914 and the first fifteen ordered in October, the first boat (UB 1) being built in a hundred days.67 Initial numbers were kept small so that lessons learned in their operation could be applied to later units. Given intense pre-war German interest in minelaying, work also went ahead on a long-range minelayer, the design of which (Project 38) was completed on 5 January 1915. The project was designated UE because it was ordered under War Contract E. Like the UB- and UC-boats, UE was conceived for quick production, with a single low-powered diesel. Like the earlier small submarines, this one was intended for completion before the end of the war, which in January 1915 was not expected to last past the autumn. That calculation may have taken the initial unrestricted submarine campaign into account. UI planned on building ten by the end of 1915, but initially only four were ordered (U 71–U 74).
For the US Navy the greatest war prize was surely German diesels, which grossly outperformed anything in US or British service. U 140 was powered by two ten-cylinder MAN four-stroke engines plus two six-cylinder battery-charging engines. The post-war US Navy copied the MAN diesel engine at the New York Navy Yard and installed its version on board many ‘S’ class submarines. Under the provisions of the Versailles Treaty, the Germans were not permitted to export military materiel, so there was no question of license production. US naval intelligence noted angrily that the Japanese had no such scruples (their initial long-range submarines were based on German designs) and within a few years the US Navy was considering buying German naval equipment. This photograph shows the engine room of U 140.
By mid-February it seems to have been accepted that the war would continue, even though the effects of the U-boat campaign had not yet been felt. The UI was authorised to let a new round of orders. It designed a larger torpedo-armed version of UE which it called UF, but that mass-production U-boat was rejected by the Navy Office in favour of the current standard Mobilisation type. At the same time six more UE were ordered (U 75–U 80). The new Mobilisation boats were simplified for quicker production, but only three out of the initially projected six (U 63–U 65) were ordered (March 1915).68 Their eleven-month construction time was a German First World War record.69
Germany opened the first unrestricted submarine campaign with a limited fleet; on 1 April 1915 there were only twenty-seven operational ocean-going U-boats. Only boats already under construction could participate; the UI estimated that as late as 1 July 1916 it would have only forty, counting likely losses. At the time, it was estimated that a full blockade of the United Kingdom would require forty-eight U-boats equivalent to the Mobilisation type. To that had to be added twelve for the Baltic and twelve for the High Seas Fleet, under the direct command of the High Seas Fleet U-boat commander (FdU). Given likely wastage, the UI estimated that another thirty-two U-boats would be needed.
The UI presumably knew that it had no chance at all of a crash programme, so it couched its April 1915 proposal for a greatly-expanded U-boat in terms of a target date of 1924. Experience to date showed that U-boats needed higher surface speed and greater endurance at sea (including better habitability), which meant larger engines and greater unit cost. To replace the Mobilisation type, the TI looked back at a Project 31 design begun in 1913 as an alternative to the closed-cycle steam submarine it was then building. In its current incarnation it would be powered by new-generation 1500bhp MAN and Germania engines.70 The TI planned forty-six such boats, the first six (U 81–U 86) to be delivered as quickly as possible, the rest at the rate of one per month. Because these boats required new design effort, it was quicker to continue building Mobilisation boats (Project 25) to a modified design with four rather than two bow torpedo tubes than to switch designs. In May 1915 the UI asked for five more Mobilisation boats on an immediate basis, later increased to six: U 87–U 92. These submarines began a rolling programme of new Mobilisation type construction (with gradual improvements) in five- or six-boat batches.71 A parallel programme developed improved coastal U-boats (UB II and UC II [Project 41] classes). Project 41 in particular extended these boats beyond the North Sea; one of the design requirements was that it be able to reach Austro-Hungarian bases. The failure of the spring 1915 offensive and of the initial U-boat campaign made it clear by the summer of 1915 that the war would last at least another year, so follow-up contracts for improved coastal U-boats were let.
Project 31 was abandoned, but not the search for greater endurance and performance. A new Mobilisation design was developed: Project 42. It grew from about 760 tons to 1200 tons in a single jump. To achieve the desired high surface speed, the two main diesels (1650bhp to 1750bhp) were supplemented by two battery-charging diesels (450bhp each), so that the entire power of the main engines could be devoted to surface power. Project 43 was considered a U-cruiser (10,000nm range at 8 knots) and was given a 10.5cm gun so that it could, if necessary, comply with the Prize Rules and attack on the surface. The design was presented to the Navy Office in December 1915. After a series of delays, the first contracts were let in May 1916. Meanwhile a new smaller Mobilisation U-boat design (Project 43) was also completed. One of its supposed virtues was that it could introduce a new builder to the greater complexity to be expected of Project 43.
Projects 42 and 43 were too large for the mass production needed to support a new U-boat campaign. In April 1915 the UI had called for a simplified 600 ton type. With unrestricted submarine warfare renewed (as it turned out, briefly) early in 1916, the project became more urgent. The new design (UB III [Project 44]) was based not on the Mobilisation boats but rather on the smaller UC II minelayer, its mine shafts replaced by four torpedo tubes with two reloads. The engines were more powerful than those of a UC II, but still far short of the expensive ones in a Mobilisation boat or in the new types. Since engines were the great bottleneck in production, in April 1916 the UI ordered enough for twenty-four submarines; boats were ordered the next month (UB 48–UB 71).72 The first units were delivered in the summer of 1917.
In February 1916 the Admiralstab submitted a plan for unrestricted submarine warfare against Britain to the Kaiser. This was considerably more ambitious than the UI plan laid out in 1915. The Admiralstab envisaged twenty-seven U-boat operating areas (stations) around the British Isles; to occupy them would require 170 ocean-going boats (taking losses into account) based on the Heligoland Bight. Another twenty would be required for operations with the High Seas Fleet and to patrol the Baltic. With a 10 per cent reserve, that made 209 ocean U-boats. Another thirty UB-boats (improved type) would be used both to keep British minelayers and submarines out of the Heligoland Bight (so U-boats could get in and out). Twenty-five more would protect the coast and operate out of Flanders.73 Other requirements were minelaying against England (fifty-four large and seventeen small U-boats), minelaying against Russia (ten large and twenty small boats), Baltic operations (other than patrolling the newly-conquered eastern territories) and Mediterranean torpedo and mine operations (thirty-five ocean-going torpedo U-boats, eleven small torpedo U-boats, ten ocean-going minelayers and six small minelayers). The totals were 270 large and ninety-six small torpedo U-boats and seventy-four ocean-going and forty-three small minelayers. This must have been breathtaking. Even the UI, in stating a big long-range programme in April 1915, had been content with 154 ocean-going torpedo U-boats and another forty-six minelayers and coastal boats. The reality was worse: as of 1 January 1916 U-boats built and building amounted to seventy-five ocean-going torpedo U-boats, forty-four small torpedo U-boats, ten ocean-going minelayers and four small minelayers. The requirement was so far beyond capability and the resources so thin, that the calculation had no impact, except as an indication of what the Germans actually thought an unrestricted campaign required.
Early in 1916 the UI designed a longer-range minelayer (Project 44) based partly on its new ocean U-boat (Project 43), but with mine stowage adapted from the earlier and much smaller Project 38 minelayer. Submerged range was less than that of a Mobilisation U-boat because the mines took up space which would otherwise have gone for fuel. In April 1916 the UI and the Navy Office laid out contracts for delivery in 1917. The UI decided to stop building Mobilisation boats (the last of which would be delivered in the summer of 1917), shifting to the new types. There was sufficient capacity for twenty-four Project 42, but instead the UI planned twelve Project 42 (U 127–U 138) and ten Project 45 minelayers (U 117–U 126).74 Unfortunately it was soon evident that the big new U-boats would take longer to build than expected, leaving a three-month gap in deliveries between the summer and autumn of 1917. With two or three large U-boats being lost each month, the UI decided to let an immediate contract for twelve more Mobilisation boats (U 105–U 114). The initial twenty-four UB IIIs (UB 48–UB 71) were ordered for delivery in the first quarter of 1917. With the contracts for the Mobilisation boats and the big U-boats let, the only remaining capacity was for UB IIIs, so UB 72–UB 87 were ordered in September 1916.75
While all this was happening, the Germans’ second attempt at unrestricted U-boat warfare was collapsing due to US pressure after an April 1916 incident. The Prize Rules were reinstated. Since the presence of so many warships in the Channel and the North Sea made that dangerous, interest turned to more distant waters. The Admiralstab asked the TI to design a U-cruiser capable of fighting an armed merchant ship, which up to that point had been an antidote to any U-boat operating on the surface. Although the trade campaign soon collapsed altogether (U-boats were reassigned to support the High Seas Fleet directly), the project survived, since it was reasonable to assume that operations under the Prize Rules would soon resume. In May 1916 the Admiralstab asked the UI to design and built a big long-range high-performance U-boat: Project 46. As usual, the problem was to provide enough power. MAN was sketching a 3000bhp diesel, but for the time being the designers had to make do with the current 1650–1750bhp type (there could be no question of steam power, as in the British ‘K’ boats); surface speed was only 14–15 knots. Range was 12,000nm at 10 knots. In August the UI awarded contracts for three U-cruisers (U 139–U 141).76 In October, when the order was given to resume trade warfare under the Prize Rules, the Navy Office wanted more U-cruisers, so it asked how many could be completed by the spring of 1918. The UI ordered nine more: U 142–U 150 to a slightly modified design (Project 46a).77 Construction of some of the Mobilisation boats was deferred in favour of the new U-cruisers.78 British intelligence became aware of this project; in the autumn of 1916 Admiral Jellicoe and others wrote about the expected extension of the U-boat war to North and probably to South America.
At the other end of the scale, the Germans built small submarines of the UB series, initially to operate out of the new base in Flanders. The next series were ocean-going submarines well suited to the North Sea. UB 88 is shown at Mare Island on 23 September 1919. Submarines of this type operated extensively in the Mediterranean.
The UI was also interested in something with better protection, which it called Project P (Panzer, armoured): Project 47. In June 1916 it sketched such a submarine, which would require the projected 3000bhp engines.79 Compared to Project 46, which was already expensive, Project 47 would have cost twice as much, with twice the crew and slightly greater surface endurance. Project 47 was probably offered during the autumn of 1916 to High Seas Fleet commander Admiral Scheer. After Jutland and particularly after his August 1916 sortie, he became convinced that he wanted fast powerful U-boats to provide direct support, in much the way Jellicoe had demanded the ‘K’ boats more than a year earlier. Project 47 was still more or less alive in May 1917, but by then the UI was also interested in something smaller but much faster: Project 50 (K44, the K presumably indicating a cruiser [kreuzer]). Just like the British ‘K’boat, it needed steam power to achieve high surface performance.80 One boat was ordered under War Contract AA (February 1918) as UD 1, but at the end of the war it had not been laid down, overtaken by the priorities set by the unrestricted submarine campaign.
However, in the autumn of 1916 orders were issued for resumed trade warfare, this time under the Prize Rules. As initial steps U 63–U 65 were given greater fuel capacity, the U 71 class minelayers were provisionally ordered converted to torpedo submarines and all ocean-going U-boats were ordered armed with 10.5cm rather than 8.8cm guns. The big Project 45 minelayers would have one 15cm gun in place of the earlier pair of 10.5cm weapons. Ultimately the campaign should employ longer-range U-boats. In 1916 the Germans already had some experience in that direction, with a group of cargo-carrying U-boats built specially to evade the British blockade. One of them, Deutschland, made two highly-publicised (and commercially successful) visits to the United States. A sister-ship, Bremen, was already complete (she was lost on her first trip) and six more planned. With the shift to Prize Rules warfare, necessarily in distant waters, the big cargo U-boats became attractive as potential U-cruisers, which could be armed with 15cm guns. In December 1916 four cargo U-boats were taken over as U 151–U 154. Once unrestricted submarine warfare was resumed, the other three were taken over as U 155–U 157.
Within a few months the Kaiser agreed to resume unrestricted submarine warfare. Now smaller U-boats were once again very well worthwhile. From UI’s point of view the important point about the new campaign was that it was personally supported by chief of the army high command (OHL) Field Marshal von Hindenburg. In January 1917 von Hindenburg and his chief of staff General Erich Ludendorff in effect controlled German industry in support of the land war. Their strong support of the U-boat campaign, which they sometimes called Germany’s ‘last card’, caused them to send an officer to UI in Kiel in January 1917 specifically to ask its problems and to agree on solutions in terms of making material and labour available. UI convinced the OHL to approve immediate contracts for more U-boats: twenty-five UB IIIs for the middle of 1917, plus another ten UB IIIs and twenty-eight Mobilisation boats by the middle of 1918 and another seventy boats of various types by the end of 1918. At this point the Navy Office did not want to order any boats which might be completed after the beginning of 1918, on the ground that they would overburden the navy budget. In effect its new connection with OHL gave UI an end-run around the Navy Office which up to that point had run German naval shipbuilding. The overburdening most likely referred to the Navy Office’s hopes of completing capital ships.
The UI almost immediately began ordering UB IIIs, replacement UC IIIs and a few Mobilisation boats and U-cruisers.81 Production was slowed by crippling shortages of raw materials (which can be attributed to the British blockade) and to severe labour shortages (partly due the demands of the army for ever more men). Given the OHL connection, in July 1917 the Navy Office asked the War Office to give the submarine programme priority over all others. In exchange it finally had to cut its surface ship programme, transferring all skilled workers to U-boat construction.82 This step unfortunately roughly coincided with the beginning of the convoy operations which made U-boats far less effective.
Once U-boats were given the highest priority, ninety-five more of existing designs were ordered: thirty-seven UB III, thirty-nine UC III, ten U-cruisers and nine Mobilisation type boats.83 All were scheduled for completion between the summer of 1918 and January 1919. In hopes of increasing production, in the autumn of 1917 UI designed a new 364-ton single hull boat (UF, Project 48a) specifically for the Flanders Flotilla, in effect a replacement for UB III.84 Due to previous construction and to limited losses due to ineffective anti-submarine warfare, the U-boat force peaked in October 1917 at 140 units. By that time the convoy system and other anti-submarine measures were becoming effective. Moreover, the number of U-boats in commission was several times the number active at any one time.85
Scheer was not convinced that the U-boats were losing. By the late autumn of 1917 the Admiralstab finally had executive authority over all naval forces and in November Scheer pressed its chief to create a U-boat Office directly under his operations directorate. Scheer believed that the Estimates Department in particular was holding back orders for sufficient U-boats. In November 1917 its head expected that the navy would receive eighteen U-cruisers and sixty other U-boats during 1919, a figure he considered adequate. Almost everyone else present disagreed. By this time sixty-three submarines had been lost in 1917, so it seemed likely that another 102 would be lost in 1918. The proposed programme would not even replace them, even though U-boats might be Germany’s only effective offensive weapons. The UI thought that yard capacity was 118 submarines, including twenty-two U-cruisers. However, instead of a single U-cruiser, three UB III or four UC III or five UF-type submarines could be built. Another twenty-four single-hull UF-boats could be built (the Head of Estimates disagreed).
This argument brought in OHL, because it might be possible to increase production if the army could release labour. Ludendorff pointed out that he was finding it difficult to replace his own losses. By this time, moreover, Russia was in turmoil and Ludendorff was probably beginning to think about a new ‘last card’, the massive Western Front offensive he launched in April 1918. That required not only troops but also new munitions, for which he had to allocate the same labour the navy wanted to build U-boats. The autumn programme was finally set on 17 December 1917: 120 units, consisting of thirty-six UB IIIs, thirty-four UC IIIs, twenty UFs, twelve Mobilisation boats and eighteen U-cruisers.
The Russian collapse made it possible to shift some Baltic yards to submarine construction. Scheer’s U-boat Office came into existence in December 1917 and the following January it began awarding contracts for a big UF programme, as that was the simplest type to build.86 Efforts to subcontract were finally proving effective. However, the demoralisation of German society traceable to the blockade was also having an effect. Workers were refusing overtime. Strikes and absenteeism were increasing. The summer 1918 influenza epidemic was particularly damaging because of the workers’ inadequate diet. Labour was also being stretched. For example, the UI estimated that 185,000 riveter worker-days were needed during 1918 at Germania, but only 145,000 were available. One yard offered to increase production by a third if they build only one type of boat and went to full day and night shifts – if only they could get 3000 to 4000 more workers.
Meanwhile, with the extension of convoys it seemed that U-boats would have to work further afield, beyond the range even of Project 46a. An enlarged version (3000 tons) would be able to steam 20,000nm at 8 knots and thus could reach the Gulf of Mexico and even Brazil. A new programme was proposed in May 1918: two 3000-ton U-cruisers, six modified Project 42, thirty-six Mobilisation boats, fifty UB IIIs, thirty-five UC IIIs and thirty UFs. It is somewhat surprising that both UB III and the similar UF were to be bought. Formal requirements set by the new U-boat office in June 1918 were: forty-four UB IIIs (War Contract AB), forty UC IIIs (War Contract AC), forty-eight Mobilisation boats (War Contract AD), sixteen large Mobilisation boats (Project 42a: War Contract AE) and forty-four UFs (War Contract AF).
Once the Spring Offensive failed in August 1918, the U-boat war seemed even more important. The U-boat office looked for ways to increase production. One option (small programme) was to draft 15,000 workers to achieve a 25 per cent increase in production at all yards. A second (the large plan) was to draft 50,000 workers for a 70 per cent increase in production in eighteen months. A third was to transfer all contracts for minor warships (torpedo boats, minesweepers and armed trawlers) to yards in occupied territories, freeing all Reich yards to build submarines. Yet another possibility was to use Austrian yards, whose capacity was thought to be thirty-seven UB IIIs. It might be possible to double the current rate of 12.7 U-boats per month by the end of 1919. On 30 August the requirement to achieve the 25 per cent increase was immediate drafting of 20,000 skilled workers as of 1 October, to be followed by another 30,000. Another 70,000 were wanted later. On this basis the U-boat Office expected to increase the planned delivery of fifty-four large and 133 smaller U-boats between October 1918 and the end of 1919 to seventy-four large and 188 smaller ones, with even more possible if the 70,000 men could be made available. As the situation on the Western Front deteriorated, it became more difficult for the army to release men, or to limit its demands for fresh men.
On 11 August 1918 Admiral Scheer became head of the Admiralstab, which now meant that he was head of the whole navy. He considered the U-boat campaign paramount; in his eyes it was the only offensive arm left to Germany. The Large Programme became the Scheer Programme. Scheer pressed Ludendorff for the men the U-boat Office wanted. The army had bled badly in the failed offensive and the subsequent retreat and it badly needed new men. For his part Scheer considered the ‘small’ building programme inadequate in the face of improved Allied ASW as well as new Allied merchant ship construction. He decided to limit the number of distinct types and he pressed for American-style mass production, which would bring in many firms outside the traditional shipbuilding business. To keep sinking more ships than the enemy could build, Scheer needed a lot more U-boats. His goal was to increase the monthly total from 12.7 to 16 in the fourth quarter of 1918, to 20 in the first quarter of 1919, to 25 in the second quarter, to 30 in the third and to a steady 36 from the fourth onward. Even if this was possible, Scheer faced a considerable crew shortage and a fuel-oil shortage.
As late as early October 1918, it seemed that Germany might be able to stabilise the Western Front. The Germans would be able to shorten their front and they might be able to release men to the U-boat industry by mid-November. For a time Hindenburg and Ludendorff imagined a new stand-off on land in which the U-boat offensive provided Germany with the necessary leverage to force an acceptable settlement. Plans were therefore drafted for a 1919 programme. It seemed that enough UF had been ordered, so the UI designed an enlarged version (UG, Project 51), with better surface performance.87 C-in-C U-Boats wanted a new minelayer, so the UI developed what it called Type I. The Mediterranean commander liked the UB III as exactly what he needed, so he wanted more of them (other officers considered UB III obsolete). Ultimately, in early October, the types favoured were the large Mobilisation boat (Project 42a), the Mobilisation type, UG, UC III and a large minelayer of unspecified type (fifteen to be built). The ratio of the other types was to be 1:2.5:4:1.5, actual numbers depending on industrial capacity. On 29 October 1918 the Admiralstab announced that all surface ships to be completed after the beginning of July 1919 were to be cancelled in favour of maximum U-boat production. By that time the main competitor with Scheer’s programme was a plan to produce 1000 tanks beginning in November 1918, which would have cut U-boat production by about 30 per cent by mid-January 1919. There was, however, insufficient fuel for the tanks.
By this time the situation was beginning to crumble. None of the big 1919 programmes every came close to fruition. By November 1918 Germany was short of resources. Fuel that was too scarce to run tanks was also too scarce to run aircraft and it was probably scarce because heavier oils, on which submarines ran, were also scarce. The Western Front might be stabilised, but elsewhere around Germany allies were defecting and the German army would have had to cover the frontiers around the country. The slight manpower surplus Scheer imagined for November 1918 would have been much more than wiped out. Even had the High Sea Fleet not mutinied, it seems that the blockade had badly undermined German society, so that the kind of intensive effort on which Scheer relied would have been impossible.
For anyone looking ahead to a new U-boat war, the lesson was obvious: the Germans had started too late and had taken far too long to get their priorities straight. The whole idea of defeating Britain by sinking merchant ships might or might not have worked, but the campaigns of 1915–16 had given the British far too much time to understand the problem. That the British had failed to adopt convoy tactics earlier had made it possible for the Germans to mount a third campaign in 1917, again with insufficient forces. Remarkably, the Germans began the Second World War with another very small U-boat force, although this time it had effective ways of dealing with convoys.
The UC series were the minelayer equivalents to the UBs. UC 97 (UC III type) is shown visiting Toronto on 10 June 1919 during a post-war bond-selling tour of the Great Lakes. The object under her conning tower is a torpedo tube; her fore end was occupied by minelaying tubes. She also had a torpedo tube right aft. The gun was a 10.5cm/45. Alongside the submarine is a fleet tug. (RCN)
By 1917–18, smoke screens seemed to be the best way to prevent U-boats from seeing ships in convoy, hence the best way to prevent attacks. This smoke-screened convoy was photographed from the air in June 1918.