WAR EXPERIENCE
If Britain had entered the First World War because the rise of German sea power was a mortal challenge, in 1918 the two rising sea powers, the United States and Japan, were potential future enemies. British naval rhetoric, both within and beyond the Admiralty, often referred to both. However, from the beginning, it seems to have been accepted that war against the United States was unlikely to the point of being nearly impossible, whereas war against Japan was quite possible. The requirements of such a war shaped the inter-war British fleet, much as the requirements of war against Japan shaped the inter-war US fleet. For both the Royal Navy and the US Navy, the stated possibility of war against the other had important advantages. Success against Japan would demand a considerable edge in naval power, at the least because of the vast distances involved, but after the First World War, the British and US governments and populations had little taste for naval expenditure. Given a declaration that the navy was intended mainly or solely to deal with Japan, the government of the day could demand that the navy cut down to parity with the smaller Japanese navy – which would be fatal in the event of war. Also, having a nominal opponent whose capabilities were relatively openly known made it far easier to guess what had to be done to maintain a fully modern fleet. Japan was far too secretive for that.
From a strategic point of view, the greatest surprise of the First World War was the enormous dislocation caused by a handful of German light cruisers operating against British trade in 1914–15. The war showed that seaborne trade was the single most important naval target in the British Empire. The two threats were surface cruisers and U-boats. U-boats had been effective mainly near ports, because they had limited mobility, hence could not easily search the broad oceans (in the Second World War the Germans would solve that problem with radio intelligence and wolf packs). In the Pacific the likely main future threat to British Empire trade would be cruisers and other surface raiders. The British tried and failed several times simply to outlaw submarines. Many believed that by violating the pre-1914 rules of blockade when adopting unrestricted submarine warfare, Germany had in effect committed suicide by drawing the United States into the war, so when planning a war against Japan in the 1920s, American officers rejected a strategy of such warfare for fear that it would bring Britain, with the largest merchant fleet in the world, into the war (this reason evaporated in 1941, and unrestricted submarine warfare played a major role in defeating Japan). These considerations made cruisers a primary threat to trade, and focussed inter-war British cruiser thinking heavily on the needs of trade protection. The British did not dismiss the possibility of war in Europe, but it was clearly a lesser problem.
By 1918 the Director of Naval Ordnance was convinced that cruiser guns should be enclosed and power-operated. His first step in that direction was the prototype enclosed mounting on board HMS Diomede, shown on 10 July 1929. (Photo by Allan C Green via State Library of Victoria)
Against the new problem of war against Japan, Britain after 1918 clearly lacked the financial resources she had enjoyed in 1914. In August 1919 the planning assumption that there would be no major war for ten years was introduced: the ‘Ten Year Rule’.1 The Admiralty interpretation was that the fleet had to be modernised by 1929. Because the existing fleet had been designed for a North Sea war, that implied a major new construction programme, particularly in cruisers (see the next chapter). The British government had nothing like that in mind. It tolerated Admiralty calls for new cruiser construction, but it avoided long-term programmes designed to build up the large cruiser force envisaged.
The great wartime tactical surprise was that actions so often turned into chases. Before 1914 it was assumed that the enemy fleet would seek battle. However, the German fleet, and German naval forces in general, fled if they did not enjoy an overwhelming advantage. After Jutland, for example, the British sought a new kind of battleship shell which could stop a typical German battleship, that being the first step needed in forcing any sort of decision. The last cruiser design of the war, the ‘E’ class, was conceived to fight a chasing action, with a combination of maximum speed and maximum ahead fire.
Actions would normally be fought at maximum range, far beyond what had been envisaged for cruisers before the war. That happened in 1914 at the Falklands. The maximum-range argument also applied to chases, because longer gun range could make up for any slight deficiency in speed. Giving cruisers longer gun range meant giving them the same sort of sophisticated fire-control systems which were being developed for new battleships.
The Post-war Cruiser Force
Pre-1914 discussions of a ‘one power’ or ‘1.6 power’ standard had always omitted the US Navy. The US entry into the First World War in April 1917 suggested that the United States could no longer be omitted from British strategic calculations, and by 1919–20 the Admiralty was promoting a ‘one power standard’. Whether or not it had any expectation of fighting the United States, this approach guaranteed an essential margin over the more likely enemy, Japan. Thus there could not be enough navy to send a fleet to the Far East and to retain a sufficient deterrent fleet in European waters – exactly the problem which would bedevil the British in 1939–41. The Admiralty therefore promoted a strategy of ‘naval mobility’. It demanded wholesale adoption of oil fuel, and the build-up of sufficient reserves throughout the Empire. Calculations of the necessary reserves were a staple of Admiralty planning throughout the inter-war period.2 They focussed on the requirements of war in the Far East. The shift to oil fuel also required that the Royal Navy protect the routes from the sources of oil, hence that the fleet had to be larger than in the days of coal produced in the British Isles. In the 1930s there was some public interest in reversion to coal, and DNC and E-in-C had to demonstrate (for internal consumption) that ships so fuelled would have neither the speed nor the endurance of those burning oil. Because it had a global chain of bases, at which ships could fuel, the Royal Navy had little interest in fuelling at sea.
Converted to a gunnery training ship, Diomede no longer had any need for her special enclosed gun mount, so it was replaced by a standard open 6in gun. The ship is shown in the Firth of Forth, 25 October 1943. Note the twin power Oerlikon at shelter deck level under the bridge.
Calculations of fleet shape assumed that cruisers would be organised in five-ship squadrons, and usually a 25 per cent margin was allowed for refits. The earliest estimate was developed by the Admiralty Reconstruction Committee, formed in February 1918 to decide the appropriate shape of the future Royal Navy. Early in 1919 it envisaged three main fleets (Atlantic, Home and Mediterranean) plus a China Fleet built around a single battlecruiser. One cruiser squadron would serve with each fleet, and the Atlantic and Mediterranean fleets would have one extra cruiser to serve as the destroyer commander’s flagship. In addition, each of four stations (East Indies, Cape of Good Hope, South America, and Western Atlantic) would have one cruiser squadron. That made eight squadrons, forty (actually forty-two) ships, requiring a total of fifty active ships; the committee wanted another ten in reserve. Given the wartime needs of the Grand Fleet, the allocation per fleet was quite small. This calculation probably explains an offhand remark by Admiral Beatty at the Washington Conference (1921) that the Empire needed about fifty cruisers. After the desired number was set at seventy a few years later, as Chancellor of the Exchequer Winston Churchill used Beatty’s lower figure as a debating point.
Attention shifted East. In 1918 the Dominion Prime Ministers invited Lord Jellicoe, who after commanding the Grand Fleet had been First Sea Lord in 1916–17, to tour the Empire to advise them on naval defence. Jellicoe left with his staff aboard HMS New Zealand on 21 February 1919, returning home that autumn. The First Lord of the Admiralty Sir Eric Geddes omitted strategy from the sorts of recommendations Jellicoe was to provide, but inevitably he developed a strategic framework. He considered Japan the only likely threat to the British Empire in the East, citing Japanese acts and statements during the First World War. Jellicoe laid out the basis of inter-war British naval strategy: a main fleet based in the East. No base had the infrastructure (or the specialist personnel) to support such a fleet in peacetime, so for a time between the outbreak of war and the arrival of the fleet the Japanese fleet would be more or less free to act, for example to attack Australia. The long Eastern trade routes would require convoy protection. Jellicoe identified Singapore as a potential fleet base, but pointed out that without fortifications it could be taken by a large Japanese landing force. He envisaged creation of an Empire Pacific fleet including ten cruisers to form an ‘A-K Line’ plus another fourteen (and thirty-seven armed merchant ships) for convoy work. Given his wartime obsession with enemy torpedo attack, and the role of cruisers in dealing with it, Jellicoe seems to have understated what the future main fleet needed, perhaps to limit the cruiser requirement.
From the Dominions’ point of view, Jellicoe’s most important conclusion was that while the United Kingdom would provide the battle fleet (including its cruisers), the Dominions should provide the trade-protection cruisers. In fact there was no real prospect that the Dominions would provide the numbers Jellicoe stated, let alone the much larger ones later proposed. The Canadians showed little interest in a trans-Pacific threat, and the Indian Government concentrated on the Russian threat from the north. Australia alone was unlikely to build a large enough fleet, and New Zealand had much smaller resources. South Africa had only a limited interest in building a navy.
The Admiralty professed itself unhappy with Jellicoe’s report, but it reached much the same conclusions. Possibly Jellicoe had been too explicit in dismissing any American threat, hence making it difficult for the Admiralty to explain to British politicians why the Royal Navy should be much larger than the Japanese. The Admiralty certainly did adopt the idea that trade-protection cruisers should be provided, at least for the Far East, by the Dominions there. Thus post-war discussion of the trade-protection cruiser were headed ‘Colonial Cruiser’. Although Admiral Jellicoe himself soon left to become Governor-General of New Zealand, his Chief of Staff Captain F C Dreyer resumed office as Director of the Gunnery Division (DGD) of the Admiralty. In that capacity he was deeply involved in formulating the characteristics of the post-war cruisers.
In 1921, when the ‘Colonial Cruiser’ (soon to become the 10,000-ton 8in cruiser) was being discussed, the idea was raised that the threat of such ships against Japanese seaborne trade could help tie down Japanese naval forces until the main fleet arrived. The Germans had demonstrated exactly that possibility with their Emden and other small cruisers in 1914–15. The raider threat presented by the British would also help protect their own trade. Within a few years planners apparently saw cruiser trade protection mainly in terms of running down raiders; almost all convoy escorts would be armed merchant ships taken up from trade. By 1924, the naval staff had concluded that to fight a war in the East the Royal Navy needed seventy cruisers. Unfortunately no credible explanation has survived, but at times it was stated that twenty-five were for the fleet and forty-five to protect trade.3 Each figure included the 25 per cent refit margin (and no explicit margin for losses). On this basis an explanation can be deduced. The fleet required the ‘A-K’ Line (ten cruisers, two squadrons) and two more squadrons for pro- and antidestroyer work, a total of twenty ships (with the margin, twenty-five). The Royal Navy stationed two cruiser squadrons in China, both for security and, given the new idea of pro-trade raiding, as a sacrificial force to hold the area until the main fleet arrived. Other squadrons were needed in the South Pacific (Australia and New Zealand), in the Indian Ocean (Africa Station), and in the Atlantic (North and South as separate stations) – a total of seven cruiser squadrons, thirty-five ships. Probably a thirty-sixth was added as flagship of the Australia-New Zealand station. With the 25 per cent margin, that made forty-five ships.4 The seventy-cruiser figure became a driving force in inter-war British cruiser thinking. It included not only the Royal Navy but also the Dominion navies.
Lessons Learned Committees
Two committees were formed to collect lessons on future material: first the Fire Control Requirements committee and then the Post-war Questions (PWQ) Committee.5 The Fire Control Committee saw light cruisers primarily as gunnery ships, though carrying a powerful torpedo armament. Thus no increase in torpedo armament could be accepted at the expense of gun armament. It was pointless to use cruisers for torpedo attacks when larger numbers of destroyers would be more likely to succeed. It also seemed unlikely that aircraft carriers would relieve cruisers of their scouting role, which in turn would require them to carry scouting aircraft. In order of priority, cruiser requirements were numbers, speed, guns and torpedoes, and the ‘D’ class seemed to carry the right armament, although the ‘E’ class offered better speed and sea-keeping. An important pointer to the future was the recommendation that capital ships use dual-purpose guns as their secondary armament, preferably in dual mountings (to reduce personnel) using QF weapons. This reasoning affected light cruisers, with their anti-destroyer mission, as much as capital ship secondary batteries. Eventually a 5.1in and then a 5.25in gun was chosen for battleship secondary armament – and thus as a cruiser main battery.
The Committee considered the number of main battery fire control positions in modern capital ships and cruisers excessive (though secondary control might be deficient); torpedo control positions could be reduced. Ships should have a plotting room below and behind armour containing their fire-control computer (Dreyer Table or the planned automatic computer); it would also provide torpedo control. The Committee proposed a director control tower (DCT), to carry the director, its personnel, the spotting and rate officers, and a rangefinder, as the only way to simplify above-decks control arrangements.6 The DCT would be mounted atop the bridge, eliminating the usual heavy tripod carrying a fire-control top and a director. It combined all the fire-control instruments in such a way that it was impossible to train any of them on anything but the correct target. The Committee envisaged a cruiser bridge stiffened to carry the DCT atop an extra tier at its after end, the rest of the platform carrying the night defence fire-control instruments formerly carried in the foretop. The torpedo control and firing position should be on the level of the navigating bridge and abaft it, with searchlight control from the torpedo control positions. A second DCT would be mounted aft, as well as duplicate torpedo controls. By the time the committee reported, a mock-up DCT was being built at Portsmouth. The DCT became a key feature of post-war British warships. The prototype was installed on board HMS Enterprise. In later ships the DCT was associated with the new automated fire-control computer, the Admiralty Fire Control Table, but not in Enterprise, which had the earlier Dreyer Table. The Committee also wanted a 12ft torpedo rangefinder (for long-range ‘browning’ shots) on each side of the bridge. The foremast should be well abaft the bridge, to avoid transmitting vibration to the bridge, and to reduce interference with the director.
For the Royal Navy, the First World War was a radio war; wireless (radio) intelligence made an enormous difference, providing both ocean surveillance and an ability to detect enemy ships beyond the horizon. The Royal Navy distinguished between navigational (safety of ships and aircraft) and strategical (location of own and enemy ships and aircraft) direction-finding; the former required much greater accuracy than the latter. However, the latter required something more, rapid search and quick sense finding. After the First World War the Royal Navy seems to have led all others, by a wide margin, in providing its ships with radio direction-finders. By the mid-1930s, sets were designated by pairs of letters, the first indicating the type of aerial and the second the frequency band. First letters were A (Adcock), F (fixed frame), L (loop), and R (rotating frame coil). Second letters were A (alternative HF and MF), C (common aerial, usable for HF or MF, with a receiver which could handle both bands using two aerials at once), H (HF only), M (MF only), and S (simultaneous use on HF and MF), of which the S series did not yet exist. Numbers indicated different sets within a series. Although navies had adopted high-frequency communication, they generally still used medium frequency (MF) as well. This one was aboard HMAS Perth, photographed (probably in New York) on her delivery voyage to Australia in 1939. The rotating coil (its motor is visible) served D/F Outfit LM. Perth and her sisters were scheduled, in 1939, to be fitted with Outfit RA, already installed on board HMS Apollo (Hobart). Outfit FC was planned for all the new cruisers of the Dido and Fiji classes and Liverpool, Gloucester and Manchester, Belfast and Edinburgh. It also equipped Kent. Further installations were planned for Dorsetshire and Norfolk, for other heavy cruisers (except Cumberland, assigned an FH), and for Frobisher and Hawkins. The earlier Southamptons were credited with RC. FA equipped Aurora and Ajax. It was to be installed on board the other Arethusas, York and Exeter, the Leanders, and Adventure. Some ships (Leander, York, Exeter, Dorsetshire, Suffolk, Berwick, Australia, Canberra, London, Devonshire, Shropshire, Sussex, Adventure, Hawkins, Frobisher, Vindictive, the Danae class, Coventry, Curlew, Cairo, Calcutta, Curacoa, Cardiff and Adventure) had Outfit SD, which used the triatic (mast) stays as antennas (it was between the funnels in Coventry and Curlew). SD and LM operated at 60 to 600 kHz. FH operated at 700 kHz to 20 MHz, and the other sets at 60 kHz to 20 MHz. The wartime HF/DF sets, which were not installed on board cruisers, were designated in the FH series, and a new VHF series was created (FV1 etc). In 1937 HMS Cornwall was credited with an FH at her foremast head, plus an LM (Berwick had SD and FH). Penelope had FM at her foremast head. LM was installed on board Arethusa and Galatea; Achilles, Neptune and Orion; Amphion and Sydney; Cornwall; and Cumberland and Suffolk.
The new cruiser Gloucester in 1939, showing her FC masthead array. The object under the searchlight, under the bridge, is a tactical and torpedo rangefinder.
Above and below: Direction-finders were retained after radar was introduced, creating some problems (the best place for the direction-finder, the top of the mast, was also the best place for the radar). Euryalus, shown as completed in 1941, illustrates a standard solution for the FC coil on her mainmast. She retained the coil as late as 1943. Note that she had a ranging radar (Type 285) for her after HA control system but not for the forward one.
Above and below: The converted anti-aircraft cruiser Coventry had an FA2 coil, initially on a tall mainmast and then, as here (in 1940), below the radar transmitting aerial on her foremast. She was converted because, by the mid-1930s, the Royal Navy was acutely aware of its limited anti-aircraft firepower. A 1921–2 naval anti-aircraft gunnery committee discussed the creation of specialised anti-aircraft ships, but that idea was dismissed on the ground that it was better for all major units to be self-defending. No such idea was even brought up when a further anti-aircraft gunnery committee met in 1931. However, the conversion of the two cruisers Coventry and Curlew seems to have been part of the anti-aircraft rearmament programme developed in the wake of the 1932 report.
About the time the final report of the Fire Control Requirements Committee was ready (March 1920), the PWQ Committee reported. For fleet work, the light cruiser had to drive in the enemy’s screen in the course of her screening duties, beat off enemy light craft trying to attack the battle line with torpedoes, and press home her own torpedo attacks on the enemy’s battle fleet. For ocean (i.e. trade protection) warfare, a light cruiser had to deal with other light cruisers, with disguised raiders, with cruiser submarines operating on the surface, and with other enemy craft. During the recent war, superior gun power was decisive in all cruiser actions fought to a finish. That the Germans rearmed their cruisers with 5.9in guns was taken as evidence that they learned this lesson. The Hawkins class outgunned enemy light cruisers, but were expensive, and could easily be outgunned in turn, e.g. by ships with 9.2in guns. It might be more efficient to reinforce cruiser squadrons abroad with the older battlecruisers than to buy more large cruisers. War experience ‘having amply proved’ the 6in gun ships, they should be developed further.7 The light cruisers had been quite successful, but although valuable in the North Sea and in the Adriatic, the destroyer-killers could not have performed the ocean work done by the ‘Towns’. Something larger was needed.
The Committee assumed that the same gun and mount would arm light cruisers and would become the capital ship secondary weapon. The Fleet favoured hand-worked guns, the largest of which was the 6in, with its 100lb shell. It was too light to get the best ballistic results out of such guns, but during the action of 21 November 1917 crews became exhausted loading them into guns high enough above the deck to give 30° elevation. Loader trials at HMS Excellent suggested that 90lbs was the heaviest projectile which could be continuously and rapidly hand-loaded (in July 1920, however, the Naval Staff chose the 6in over the 5.5in as the future light cruiser and capital ship secondary weapon). It accepted a heavier (112lb) projectile. Elevation should be at least 40°, to get sufficient range.
DNO argued that any future light cruiser should be armed with enclosed 6in mounts. The open single mounts in use had been conceived before the advent of director control, and were therefore designed for individual gunlaying. With director firing the primary means of control, visibility from the gun mounting was no longer very important. Cruisers were inherently wet, and they had limited centreline space. Length limited not only space for gun mounts, but also internal space for magazines – which, for efficient supply, should be directly under the guns. DNO began work in the spring of 1918 on a single enclosed 6in gun to replace the forecastle guns in ‘C’, ‘D’ and ‘E’ class cruisers with minimum alteration. DNO saw such a mounting as a way to keep the bow guns of the ‘E’ class dry despite their high speed. The single mounting was installed aboard HMS Diomede.
A major lesson of the First World War was the need for tactical situational awareness, using a pair of plots of the current situation (tactical and strategical). Admiral Jellicoe instituted such plots in 1914, but the idea was first really tested at Jutland (it enabled him to deploy effectively, but it did not enable him to follow the course of the battle effectively). By 1918 the Royal Navy understood plotting, and it developed the technique further between the wars. Tactical plots made possible complex tactics, including night fighting. Navies allied to the Royal Navy during the First World War all learned how to use tactical plots (the Germans were apparently totally ignorant of the idea). Plotting in turn required that a ship be able to measure the ranges to other ships with which she was not engaged. Meanwhile the Royal Navy became interested in long-range torpedo firing, which also required accurate ranges (allied navies, including the Japanese, surely picked up the idea during the First World War). Post-war, many ships, including cruisers, were fitted with tactical rangefinders outside their fire-control systems. HMAS Australia is shown on a visit to New York in the 1930s. One of her two tactical rangefinders is visible next to the base of the square tower supporting her director.
Single open mountings were ill-adapted to the high angles of elevation required for long ranges, which required higher trunnions. The loaders on the ship’s deck had to lift shells and cordite much higher. In an enclosed mount, shells and cordite were lifted by power onto a platform placed closer to the trunnions. This sort of arrangement was far heavier than the earlier open mounting, so it had to be power-trained (with manual backup). It was hand-elevated with power backup. It was hand-loaded. The weight of the electro-hydraulic motor in the gun house could counterbalance the weights of the rear numbers in the crew and of the rear overhang of the gunhouse required to provide the necessary space.
From the beginning DNO considered that only multiple mounts could make the most of a cruiser’s length. DNO preferred twins to triples because ammunition supply to the third gun would be difficult (a single hoist could easily supply two guns alternately), because the mounting would be too heavy for manual back-up training, and because a nine-gun salvo was too large for control (double salvos would be five and four guns, and a three-gun salvo would be insufficient). Unless the ship had twelve guns, the triple would not be worthwhile.8 Twin mountings (eight or ten guns) would give four- or five-gun salvos alternating left and right guns. Four mountings would suit a successor to the ‘E’ or Hawkins class (in their case, with 7.5in guns), and three would suit a ‘C’ or ‘D’ class successor. Unhappy experience with the old ‘County’ class armoured cruisers made twin mounts unpopular, but the problems of the past could be attributed to cramped design, ‘most unsatisfactory’ electric training and ammunition hoists, and poor gunsights. These guns were also in one double cradle. A new gun mount would repeat none of these errors. The PWQ Committee liked twin mounts because they saved space, simplified ammunition supply, and reduced personnel (fewer supply parties). At Jutland personnel in the open batteries of HMS Chester and Southampton suffered badly, though the guns themselves were little damaged. Gun positions should therefore be isolated and splinter-proofed.
Once loading arrangements for the enclosed gun had been thoroughly mocked-up, the two gun mounting firms (Vickers and Elswick) designed twin mounts, whose rear portions were mocked up and tested at Whale Island, with satisfactory results. The base requirement was that the two guns should be capable of being loaded and fired as rapidly as two separate single mounts. The design adopted had a short revolving trunk suspended from the turret turntable, supplied with ammunition from a fixed flashtight ’tween deck compartment (ammunition lobby) immediately below it, which in turn was supplied by a fixed hoist from the magazine and shell room. This short-trunk mounting equipped British cruisers until the Belfast class. HMS Enterprise was completed with the prototype twin 6in mount, which was also the secondary weapon of the Nelson class.
The Committee recommended an improved ‘E’ class light cruiser mounting four twin 6in, with a maximum range of 20,000yds, two turrets superfiring forward and two aft, offering a heavier broadside and heavier ahead and astern fire.9 The ship should also have two 3in antiaircraft guns (or whatever calibre was chosen for battleships) plus machine guns arranged so that three could fire on any bearing. Because the Committee recommended specifically against a specialised torpedo cruiser, it called for the maximum number of tubes for the conventional cruiser, choosing two quadruple tubes on each side. By this time quadruple torpedo tubes had provisionally been arranged for the ‘E’ class. Since the Committee considered the ‘E’ class the limiting cruiser size, it rejected any increase in protection. No bulge would be suitable, but a partial torpedo bulkhead might be worked in over the vitals. The ship should carry as many aircraft as possible, and one set of davits on each side should be capable of hoisting the smaller type of Coastal Motor Boat (motor torpedo boat).10 She should have sufficient endurance for Atlantic and Pacific operations (6,000nm at l4kts, 15 per cent less than actual endurance). Speed would be reduced from 32kts to 30kts to provide the extra oil stowage required.
The step beyond the single enclosed mount was a twin, which in the early 1920s was seen both as a battleship secondary weapon and as a cruiser primary weapon. It was tested on board HMS Enterprise. The cruiser also tested the new director control tower (DCT), which combined the functions of a director with those of a gunnery-control position. Without such a combination, it was possible for a control officer to order corrections based on splashes surrounding the wrong target. The problem returned for air spotters, and it caused real difficulties during the battle of the River Plate in 1939. In HMS Enterprise the new DCT was linked to the existing semi-manual Dreyer Table computer, but later ships linked it to the new automated Admiralty Fire Control Table, the DCT providing the table with feedback, and vice versa.
While the PWQ Committee was still deliberating, in February 1920 DNC assigned constructor Charles S Lillicrap (a future DNC) to estimate the characteristics of the proposed ship.11 Lillicrap assumed that the vitals would be protected against 6in shellfire at 7,000yds (the origin of the 7,000yd requirement is unclear). That would require 200lb (5in) cemented armour on the ship’s sides and a 50lb HT steel deck, based on sketchy information about the 6in armour-piercing (AP) shell. An ‘E’ class cruiser had an 80lb HT side included in the ship’s hull strength (80lbs for the two upper strakes for sagging and 60lb for hogging). A total of 250 tons could be saved by removing the lower strake and by moving some of the plating to the deck. The resulting deck would more than meet the requirement (Lillicrap omitted to point out that deck area was quite limited). Required additional side protection would amount to 770 tons (total 1,070 tons), hardly a trivial amount. To make the desired endurance, a new cruiser burning oil at the same rate as an ‘E’ class cruiser would need 2,600 tons of oil, giving a new deep displacement of 10,060 tons rather than 8,940 tons, this figure including 120 tons more for the additional 6in gun, ammunition, turrets, new controls fore and aft, and additional torpedo tubes. Against that, the reduced speed would cut required power from 80,000shp to 60,000shp, so one boiler room (165 tons) could be given up. That would roughly balance weight added in armament and control. Lillicrap concluded that on 9,250 tons the ship could carry another 300 tons of endurance oil, for an endurance of about 5,100nm. In effect he showed that added endurance and anything like serious protection could be very expensive in terms of ship size. DNC must have remembered his repeated wartime comments that cruisers should not depend on armour for survival.
DNC commented that to provide each pair of guns with its own magazine and shell room aft would require about 40ft more length abaft the machinery than in the ‘D’ and ‘E’ classes, due to the difficulty of arranging these spaces in the narrow after end of the ship. More space would also be needed forward of the machinery for the magazines and shell rooms and also for the larger fire-control spaces and for the larger bridge superstructure above decks. Extra length would be needed in any case to balance the greater length aft. Reduced power required might make it possible to mount all eight guns and the new control and bridge arrangements on ‘E’ class length.
A Sea Lords’ conference on 24 March 1920 concluded that a single type of light cruiser would serve for both fleet work and foreign service. It should not exceed ‘E’ class tonnage.12 Future cruiser guns should defeat 3in side armour and a 1in deck. The choice of gun calibre depended partly on elevation, because at higher elevation a shell would carry further and would be more effective against enemy deck armour. Higher elevation required enclosed gun mounts. The lightest gun which would defeat 3in side armour at 20,000yds was the 9.2in (which could defeat it out to 22,000yds); a 7.5in gun could defeat it at 16,000yds. A 6in gun could defeat both side and deck protection at 14,000yds, while the 5.5in would probably defeat the side armour at 12,000yds.
Enterprise was modernised in 1943, the most obvious consequence being removal of half her torpedo tubes. She began the war with seven 6in guns (the twin mounting forward, two in the waist, one on the centreline amidships, and two aft), three single 4in HA guns, and two single pompoms. She emerged from a large repair at Colombo (11–18 March 1941) with two 6in removed but one quadruple pompom added. By October 1942 she also had four single Oerlikons. During her major refit on the Clyde, 25 December 1942 – 31 October 1943, the two 6in were restored and the single pompoms and Oerlikons removed. A second quadruple pompom was installed, and she received six twin Oerlikons. At the same time she was fitted with major radars (Types 281, 272, 282, 284 and 285). During a short Devonport refit (3 – 29 February 1944) her catapult was removed and four single Oerlikons added. Type 650 missile jamming gear was installed during a short availability at Devonport (27-31 March 1944). The main battery ranging radar (Type 284) apparently did not work very well, and the ship was badly shaken up during a December 1943 engagement with German destroyers in the Channel. She was repaired only sufficiently to conduct shore bombardments during and after D-Day; once the army had advanced beyond the range of naval gunfire she was withdrawn and quickly reduced to reserve.
DNC and DNO argued against thinking in terms of armour protection. Jutland seemed to show that protection was a matter of chance: it took hours of 12in shelling to sink Scharnhorst and Gniesenau at the Falklands in 1914, but the three battlecruisers at Jutland, which had better armour, were all blown up by single salvos.13 On the other hand the light cruiser Conquest survived a salvo of heavy shells, all of which easily penetrated her armour. No modern British light cruiser was sunk by gunfire. Although 6in fire destroyed the German light cruiser Mainz, 6in fire by HMAS Sydney neither sank nor stopped Emden. Prolonged gunfire did sink the German light cruisers Nürnberg and Leipzig at the Falklands. Overall, ‘no absolute conclusions as to the stopping power of guns of a given size against such vessels can safely be drawn’.
Alongside the conventional cruiser, the Committee envisaged a convoy cruiser to deal with enemy cruiser submarines operating on trade routes or blockading British ports. It should have superior or equal gun power, slightly superior surface speed, equal endurance, good seaworthiness, and superior habitability. German U-cruisers devoted about 10 per cent of their displacement to machinery and fittings for underwater operation; that suggested to the Committee that a ship of about the same displacement, powered by diesels like a submarine, could enjoy superior gun power and slightly superior speed. It could be expanded to the point of being able to fight a light cruiser, though with her diesel engines she would be slower. She would have her cruiser guns on the centreline, a triple anti-submarine torpedo tube on each beam, a small seaplane scout, ‘the best submarine detection apparatus’ (with two-mile or better detection range), long-range wireless and depth charges. She could exploit her submarine detector by remaining stopped while her seaplane scouted. She could also relieve armed merchant cruisers, which during the war had been badly needed on trade routes. Nothing came of this proposal.
Anti-Aircraft Weapons
A Naval Anti-Aircraft Committee was formed in 1919.14 Its 1921 recommendations helped shape inter-war cruisers. Probably its most important was to develop an automated form of HA fire control, similar in concept to the new automated form of surface fire control, one director and its computer controlling multiple guns.15 Existing methods were manual.16 Heavy-calibre fire control required both that the shell be brought close to the air target, and also that its fuse be set (‘cut’) so that it exploded within lethal range (few if any shells would actually hit, but a near miss would shatter an aircraft). The faster the target, the more such systems were affected by inherent errors, such as delays in passing information. In 1919 fuse timing was set by a powder train whose length could be varied, but the next step was a mechanical time fuse. It could be set by a fuse-setting machine controlled by a fire-control system (such fuses were again recommended by the 1932 Naval Anti-Aircraft Gunnery Committee, and they were adopted shortly afterwards).
Like its surface counterpart, the automated British High-Angle Control System (HACS) combined a director (HADT, HA director tower) and a below-decks computer (HACS Table) in a High Angle Control Position (HACP) corresponding to the DCT and computer in a transmitting station of the LA battery. The British configuration differed from that in the contemporary US and Japanese navies, in that it separated the relatively small HADT from its below-decks computer. Initially the HADT and anti-aircraft rangefinder were separated, but they were soon combined, to preclude ranging on the wrong target (the Japanese were to have just this problem during the Second World War). Because of the connection between HADT and HACP, to increase the number of separate targets a ship could engage required not only more topside space for HADTs but also more internal space for additional HACPs. On the other hand, because the anti-aircraft calculating function was in the HACP below decks, it was possible to rig an aloft director for both LA and HA fire, an important consideration in cruisers with limited topside space. HADTs first appeared aboard the ‘County’ class cruisers and modernised battleships. Probably because the Royal Navy worked so intensively on its HACS so early, the system was badly flawed, compared to later US systems.17 As a consequence, in 1941 the Royal Navy was interested in buying the US Mk 37.
The only forms of air attack in sight were level bombing, torpedo bombing (the Royal Navy led the world in this), and strafing attacks against ships’ bridges and upperworks. Dive bombing was not considered because it did not yet really exist (except as a variation on low-level bombing). Fleet anti-aircraft fire was also expected to be important as a way of driving off enemy spotters (who would make enemy surface fire more effective) and as a way of driving off reconnaissance aircraft. During the First World War, such fire was sometimes called offensive anti-aircraft fire.
The fleet already had 3in and 4in HA guns which, it was understood, would keep attackers at such a height that bombing would be inaccurate, and would also prevent enemy spotters from staying over British ships. A ship armed only with lighter guns could be bombed effectively. It also seemed that airmen were ‘more affected by a few large shell bursting close to them than [by] a greater number of smaller shell’. Thus maximum calibre should be set only by the point at which shells became so heavy that they could not be fired quickly enough. Volume of fire was key: the amount which could be fired as long as the aircraft was in range but was not yet in attacking position. Four experimental 4.7in antiaircraft guns were on order. In 1921 the Committee recommended that four of the heaviest possible, i.e. longest-range, guns (4.7in) bear on any part of the sky, to produce a sufficient volume of fire.18 HMS Excellent, the gunnery school, considered the 4.7in fixed round the largest which could be manhandled and loaded at all elevations, although the Committee was also interested in power-loaded 5.5in and 6in guns, particularly for battleship dual-purpose secondary batteries. There was some feeling that the 4.7in would fire appreciably more slowly than the 4in, so that it might be a step beyond what was worthwhile. The 4.7in gun was mounted on board the Nelsons and the minelaying cruiser Adventure, but other new cruisers all had single 4in guns instead. All guns had to have clear sky arcs, so that four guns could be mounted in such a way that all of them could cover nearly the whole sky. The four-gun battery became standard in large cruisers. The committee hoped that a dual-purpose gun could be developed that would be suitable for capital-ship secondary batteries.
Meanwhile the Board approved increased fleet HA armament, primarily substitution of 4in for 3in guns.19 In 1920 light cruisers had first priority, the priority within that category being the Hawkins and then the ‘D’ class (those without 4in HA guns). Battlecruisers came next, then battleships. In January 1922, however, DGD asked that the subject be reviewed. At that time he planned to provide Hawkins with the same HA armament as her near-sister Effingham (three 4in). Vindictive would also have three 4in guns. ‘D’ class cruisers would have two 4in (instead of 3in) guns each, and DNO proposed the same for the ‘E’ class. More generally, DGD argued for the most powerful possible HA armament for light cruisers. Even if a ‘D’ could not accommodate more than two 4in guns, perhaps an ‘E’ could receive three of them.
Only a machine gun or machine cannon could fire rapidly enough to deal with either a nearby aircraft or a fast boat. By the end of the First World War ships had both machine cannon, such as the single 2pdr pompom, and lighter machine guns such as the Lewis gun. Pompoms were considered more effective against low- or intermediate-level bombers (as would be encountered when the ceiling was low); against torpedo bombers, which had to come close before attacking; and also against the torpedo boats and remote-control boats the Germans used to protect the Belgian coast from seaborne attack. These boats seem to have made a strong impression, because the threat of them was frequently cited during the inter-war period; pompoms were currently carried particularly because of their value against such targets.
The Committee saw light weapons as the last-ditch defence against aircraft which had penetrated the main (larger-calibre) defence. They should provide ‘almost certain defence’ at 2,000–2,500yds. The Committee favoured a multiple pompom, which offered volume of fire, since the available shooting time was so short. The 2pdr turned out to be the best gun to counter torpedo bombers and small boats.20 A six-gun mount was built at Portsmouth for further experiments and tested on board HMS Dragon in 1921–2. It was not, however, a prototype for a later service weapon. In November 1920 the Committee offered DNO its specification for the service weapon, for circulation among potential developers.21 Vickers won the contract over Armstrong (Elswick) with an octuple multiple pompom, provision for which was made in the British cruiser designs of the 1920s. The mockup was completed in 1923, and HMS Tiger carried out sea trials in 1928. The first production unit was mounted in the battleship Valiant in 1930. By that time a lighter quadruple mount (Mk VII rather than Mk V/VI) was planned for cruisers.
Lewis guns were intended specifically to deal with strafing aircraft. The Committee decided that they should be replaced because future aircraft might well be armoured. A quadruple 0.5in machine gun was developed both to supplement the multiple pompom and as an alternative where it could not accommodated. It had a much higher rate of fire (600 rounds per barrel per minute, or 2,400 rounds total, compared to 720 rounds total for the octuple pompom), but the rounds were far less destructive and the effective range shorter. Effective 0.5in range, as evaluated in 1932, was about 1,000yds (out to 1,800yds time of flight was less than for the 2pdr, but bullets were not densely grouped enough to do much damage). The gun was far inferior to the multiple pompom, but also far better than a single 2pdr. Ships also retained twin Lewis gun mounts, which were set up on a temporary basis.
The multiple pompom was developed as a direct result of First World War experience. It was the main British heavy naval anti-aircraft machine cannon of the Second World War. This octuple pompom (known as a ‘Chicago piano’) was photographed aboard the Australian cruiser Shropshire. Visible above it is the pompom director. Because such directors needed accurate rangefinding, but could not make good use of optical rangefinders, the development of the ranging radar visible here, a Type 282, had higher priority than similar work on long-range HA radars and on main battery fire-control radar. (RAN Historical Branch)
The most visible change in cruisers during the First World War was the advent of shipboard aircraft. This Sopwith Camel is aboard HMAS Sydney. (RAN Historical Branch)
It was difficult enough to launch an aircraft over a deck gun, but the advent of superfiring guns made matters far worse. HMS Dragon (about 1921) shows one solution, a hangar and flying-off platform raised above the gun mount, closed by shutters. Aircraft took off in such short distances that it might be possible to dispense with a platform over the gun itself. However, the arrangement badly affected the ship’s bridge, and it seems not to have been used in practice (it survived only because ships did not go into refit).
HMS Caledon shows a preferable solution, a rotating flying-off platform, in this case just forward of her searchlight platform.
The Committee raised the possibility that a specialised fleet antiaircraft ship was needed. A 1919 Atlantic Fleet report pointed out that the fleet should be able to concentrate anti-aircraft fire on an approaching group of aircraft, but that existing arrangements for concentration fire were ‘strained to the limit’ to deal with much slower surface targets. If concentration among battleships was impossible, perhaps a special anti-aircraft ship armed with twenty guns should be built, the equivalent of at least eight battleships. Such a ship was proposed in 1925, but nothing came of the idea.22 The steady preference through the inter-war period was to reinforce the defences of individual ships.
DGD argued that until it was possible to combine HA and LA functions in the same weapons, cruiser armament should continue to emphasise LA fire. Since cruisers were far less important than the battleships they often accompanied, it seemed unlikely that the enemy would concentrate high-level bombing attacks on them. However, cruisers were fleet screening ships, and in this capacity were intended to beat off attacks by enemy light forces – including enemy aircraft. That made their long-range HA armament important. Hence the interest in 4in HA guns, of which two should, ideally, fire on any bearing. On the other hand, the new multiple pompom was intended to defend an individual ship against attacks by aircraft and boats. It would certainly be more effective than a single pompom, but it and its ammunition would also be a good deal heavier; the added weight would better be devoted to main and heavy-calibre HA armament. Controller approved this policy on 10 February 1923, and CNS (the First Sea Lord) concurred.
Cruiser Aircraft
Despite having lost nominal control of naval aircraft to the Royal Air Force in 1918, the Royal Navy was well aware of their value. It had invented the aircraft carrier, and at the Washington Conference it pressed for a large allowance for future carrier construction. However, British carrier operating practice drastically limited the number of aircraft any one carrier could operate. It therefore became important for surface combatants to contribute combat aircraft to the fleet. To some extent this could be seen as a simple extension of the wartime placement of fighters, for fleet air defence, on board capital ships and cruisers (atop capital ship turrets and on flying-off platforms forward of cruiser bridges). The two ‘E’ class cruisers were completed in 1926 with turntable flying-off platforms. Similar platforms had been installed on board several ‘C’ and ‘D’ class cruisers, but by 1927 only that on board HMS Celedon remained. Revolving platforms were considered preferable to fixed ones because they did not require the ship to turn into the wind, but they took up more of a ship’s length. Only fighters could use them. Catapults were better because they could be used in still air and because they offered valuable freedom of manoeuvre.
The better solution was a catapult. After successful trials, in 1928 the Admiralty decided to fit catapults to all capital ships and cruisers (the ‘C’ and ‘D’ classes were later excepted). At San Diego in September 1934, HMS Norfolk shows the standard catapult aircraft of the period, a Fairey IIIF. This aircraft first flew in 1926; 379 were built for the Fleet Air Arm, and another 243 for the Royal Air Force, making it the most-produced British catapult aircraft. It could lift a 500lb bomb load, but was considered mainly a spotter and reconnaissance aircraft.
The first catapult on board a British warship was installed on board HMS Vindictive when she was converted back from a carrier into a cruiser in 1923-5. Her fixed athwartships catapult occupied ‘B’ position, the superstructure below it forming a hangar for three aircraft. Vindictive made the first British catapult launches at sea in October 1925, with Fairey IIID and Flycatcher aircraft. Her prototype Carey catapult was removed in 1926 for installation on board the battleship Resolution. As of early 1927 a heavy Farnborough catapult (the prototype F.I.H) was about to be ordered for Frobisher; apparently it was carried on board only during 1927 and possibly into 1928 (Frobisher was credited with a catapult and one spotter/reconnaissance aircraft in the April 1930 register). HMS York was the third cruiser to have a catapult, making the first British cordite catapult shot at sea in May 1928.
Policy was set out in a 1926 Admiralty memorandum.23 The limited carrier force allowed by treaty could not support detached squadrons or help protect shipping. Within a fleet, cruisers and battleships could provide supporting fighters and reconnaissance aircraft, freeing limited carrier capacity for the torpedo bombers only they could operate. Outside the fleet, cruisers would find aircraft useful in trade route protection and they could supply aircraft to support detached squadrons. Capital ships and cruisers could operate both three-seat spotter-reconnaissance (S/R) and two-seat fighter-reconnaissance (F/R) aircraft. Light catapults (for loads of up to 4,000lbs) were designed for the F/R, heavy ones for the S/R. In 1928 official policy called for installation of catapults on board all capital ships and cruisers, but the smaller First World War cruisers were never fitted.
Norfolk hoists in her Fairey IIIF, 1935.
In a fleet action, ideally two S/R would operate continuously in support of each division of heavy ships (requiring a total of five); others would support detached cruiser squadrons (Vindictive carried three). As envisaged in 1926, one S/R would be assigned to each heavy cruiser catapult. The F/R would replace and supplement S/Rs once contact was made with the enemy. For example, they would drive off enemy spotters. Plans called for eighteen of them to work with the fleet, carried on board capital ships and the cruisers of the ‘A-K’ scouting line, plus another eighteen for cruisers on detached duty. These were in addition to at least fifty fighters assigned to the fleet to attack enemy aircraft and to protect British torpedo bombers and ships (plus others assigned to the small carriers Argus and Hermes, intended for detached duties). A cruiser in the scouting line should carry an F/R. The rest of the cruisers in the fleet should carry fighters to help defend against air attack, just as their guns would help break up enemy destroyer torpedo attacks. A cruiser on trade-protection duty needed a reconnaissance aircraft and, if it could be developed, a catapultable torpedo bomber.
The 1926 memo was written as the Naval Staff was deciding that the Royal Navy could not afford separate fleet and trade-protection cruisers, so that all cruisers should be able to operate all three types of aircraft (fighter, F/R, S/R). Aircraft requirements had enormous impact on interwar British cruiser design, because catapults and aircraft stowage (if provided) demanded so much space. Further space was consumed by magazines (bomb rooms) for air ordnance. It had been assumed that cruisers would carry only one aircraft each, if that, but the new Kents had space for two light catapults, albeit probably weight for only one. It was hoped that later classes (beginning with HMS York) would have one light and one heavy catapult, and thus could accommodate one three-seat S/R and one two-seat F/R. That proved difficult, because the only available catapult positions were the usual one amidships, the top of ‘B’ turret and the quarterdeck. Experience with the quarterdeck catapult on board HMS Hood eliminated that position, while experience with HMS York showed that it was impractical to place a light catapult atop ‘B’ turret. Ships therefore continued the previous practice of placing one rotating catapult amidships, Exeter being the sole exception.
No F/R yet existed in naval service; the only fighter was the singleseat Fairey Flycatcher, which could have a wheeled or float undercarriage. The S/R was the Fairey IIID. The Fairey IIIF, which had wireless as a standard fitting, was in service a year later. The first F/R, the two-seat Hawker Osprey, entered service in 1932. By 1935 the Fairey IIIF was being superseded by the Fairey Seal, another three-seat biplane.
When the big ‘Counties’ were first completed, it was not at all clear that enough weight remained, within the Washington Treaty limit of 10,000 tons, for a catapult. HMAS Australia carried this Supermarine Seagull III on the pedestal that would later accommodate her catapult. The ship was fitted with a catapult in September 1935 (her sister followed in April 1936). (Photo by Allan C Green via State Library of Victoria)
Catapults were designated by type letter, sequence number (Roman numeral) and a suffix indicating light (L) or heavy (H). Type letters for cruiser catapults were C for Chatham Dockyard, D for double-acting (fixed, athwartships), E for a rotating extendable unit, F for Farnborough (RAE), and S for a slider (Admiralty design, cordite-operated). C.IV.H was the Carey unit in HMS Vindictive24. York had the prototype E catapult, an E.I.H. Three E.II.H were ordered in 1928, for two London class cruisers and either a heavy cruiser of the Atlantic Fleet or a third London, all to be installed when the ships came home for to recommission in 1931 or early 1932. No further catapults were immediately (1929) ordered for London and Norfolk class cruisers pending tests of other designs. E.III.H was designed to a 1930 specification, one being earmarked for HMS Hawkins. At that time no other cruisers, besides HMS Vindictive, had catapults.
It appeared that the ‘D’ and later classes could carry catapults, the Birminghams and ‘C’ class being limited at best to a revolving platform. In fact the ‘D’ class never received catapults, and the Birminghams were stricken before many catapults were made. Potential shipboard aircraft strength as projected forward to 1932 was 105 aircraft, compared to 238 on board the carriers (including one projected ship, which was not built).
Initially many new cruisers had aircraft but not catapults. In April 1931 the new heavy cruisers Dorsetshire and Norfolk each had one S/R but no catapult. Cornwall had a light S.II.L catapult (48kts) and carried one fighter (a Fairey Flycatcher floatplane); York had a heavy catapult (39kts) and carried one S/R. A year later London and Sussex carried one S/R each, without any catapult. However, catapults were being installed on board the other ‘County’ class cruisers: Exeter had two heavy E.II.H catapults (50kts) and carried two S/R; Kent, Suffolk and Cumberland each had a light S.II.L (Kent originally had an F.I.L) catapult (48kts) and one fighter; and Norfolk and Shropshire each had a heavy (50kt) E.II.H catapult and carried one S/R. A year after that (April 1933) all the ‘County’ class cruisers had either heavy or light catapults. Cornwall and Kent had light (48kts) S.II.L catapults and each carried a fighter. Suffolk, Cumberland and Berwick all had light (50kts) S.II.L catapults and each carried a fighter. Norfolk, Shropshire, Dorsetshire, London, Devonshire and Sussex each had a heavy E.II.H catapult (50kts) and carried one F/R. The new Leander had a more powerful E.III.H heavy catapult (56kts) and also carried one F/R. Similar catapults were installed in the rest of her class and on board HMAS Sydney as well as the two Australian ‘County’ class cruisers Australia and Canberra (S.II.L). Emerald and Enterprise both had light catapults, S.II.L and S.III.L, respectively.
HMAS Sydney launches her Supermarine Seagull V (Walrus) from her extending-type E.III.H catapult (note the extension). The aircraft changed cruiser catapult operations because it was designed to land in an ocean swell, thanks to its structural strength and its relatively low landing speed. It was designed to an Australian specification, then adopted by the Royal Navy as the Walrus. Total production was 746 aircraft. In effect the slow but effective Walrus became the alternative to the combat aircraft which the Royal Navy sometimes planned to operate from its cruisers. (RAN Historical Branch)
The first four Leanders all had heavy catapults. In May 1932, however, both major fleet commanders suggested that light catapults would suffice for fleet service (for either fighters or for light reconnaissance aircraft). DNAD was developing both a light reconnaissance aircraft (5,000lbs) which could be launched from a light catapult (the Fairey Seafox), and a heavier torpedo spotter reconnaissance (TSR) aircraft, which became the Fairey Swordfish. The TSR was expected to be at least as large and heavy as the Fairey IIIF, which had proven cumbersome for cruisers. The advent of the TSR probably explains the shift to the big D-series athwartships catapults and to large hangars. Cruisers equipped with TSRs typically carried three of their 18in torpedoes. The light reconnaissance aircraft carried 100lb antisubmarine bombs (to which 250lb bombs were added about 1936). DNAD argued against the light catapult, on the grounds that aircraft were becoming heavier and heavier.
Since weight was critical, saving even 10 tons by changing to light catapults was attractive. However, the same cruisers might also be needed for trade protection. DNAD argued that therefore every effort should be made to accommodate the heavy catapult. Director of Plans and Director of Tactical Duties (i.e. of Staff Requirements) supported DNAD in arguing that the heavy-catapult policy for Leanders should stand, but that proved impossible for the Modified Leanders (Amphions) and for the Arethusas. These ships were intended to receive S.II.Ls, although that decision was reversed for the Amphions (Sydney had an E type catapult and Perth never received hers).
By 1934 it was standing policy to fit all cruisers from the two ‘E’ class onwards with catapults by the beginning of 1935. In 1936 all the modern cruisers, except Aurora (which was scheduled for fitting, but never was fitted) had catapults. Hawkins was being considered for fitting at her next large repair (this was not done), and Frobisher and the ‘C’ and ‘D’ classes lacked catapults (the two ‘E’ class had recently had catapults installed). The great question was whether ships should be fitted to launch the next-generation Fleet Air Arm aircraft, weighing 12,000lbs with a 50ft span. The only projected aircraft in this category were the new dive bomber reconnaissance (DBR) and the replacement TSR, the Blackburn Skua and the Swordfish, both primarily for carriers. Both weighed about 9,000lbs and were expected to enter production about mid-1936. They would be the first cruiser catapult aircraft with real anti-ship striking power. Plans called for the TSR to be replaced by two-seat fighters (Blackburn Rocs) and possibly by three-seat fighter spotters (which never materialised). The fighter would be somewhat smaller than the TSR: 46ft span, 8,500lbs on floats. Alternatively, ships could be equipped with a large but lower-performance reconnaissance aircraft, the Fairey Seagull.
Adapting ships for the new generation of heavy aircraft entailed considerable efforts. D.I.H (fifteen built) was introduced in the ‘Town’ class cruisers and equipped them and most rebuilt ‘Counties’. D.IV.H (seventeen built) equipped the Fijis.25 These fixed catapults used below-decks machinery which affected accommodation. The design of the compact Fiji class in particular raised the question of whether aircraft were really worth the considerable sacrifices involved. Catapult and hangars took up about a sixth of the space between the main gun mountings, and they and the aircraft accounted for 190 tons in the new 10,000-ton Belfast. The 1936 London Naval Treaty removed the limit on total carrier tonnage, hence made it possible for the Royal Navy to imagine doing away with cruiser aircraft as substitutes. That left the very different mission of trade protection, for which cruiser aircraft certainly were worthwhile. For that purpose the F/R and S/R ideas were not too important. Instead, the ships could have either an aircraft designed specifically to land in an ocean swell (the new Supermarine Walrus) or an autogyro (a predecessor to the helicopter) which could land on the ship’s short deck. For cruisers which could not accommodate the Walrus, a small two-seat spotter reconnaissance (light reconnaissance, or L/R) aircraft was being developed, the Fairey Seafox. Like the Walrus, it was designed to land at low speed so that it could tolerate worse sea conditions. Unlike previous cruiser aircraft, it had no strike capacity at all. The Staff considered the autogyro so promising that they were willing to spend heavily to perfect it. DNAD, DTSD and Director of Plans all argued that the big athwartships catapults entailed too great a sacrifice in anti-aircraft firepower. Instead, ships might well revert to either a single revolving catapult or they might rely on aircraft hoisted over the side to take off as well as to land. The best way to provide the fleet with fighting aircraft was to accelerate the carrier programme. ACNS agreed. Perhaps surprisingly, Controller, who had invented the new armoured carrier, and who was certainly pressing for a larger carrier programme, disagreed. Controller estimated in 1936 that an armoured carrier cost more than a battleship, so large numbers would be difficult to build. She carried only thirty-six aircraft, so there was little prospect of distributing such ships around the world for trade protection. Catapult aircraft would still be needed in some numbers. The Fijis not only had the same hangar arrangements as their predecessors, to accommodate TSRs, but they had even more powerful catapults. The senior aircraft commander, Rear Admiral (Aircraft Carriers) wanted the battle fleet to be self-contained in spotting and action observation, so that all essential air requirements could be met even if a proportion or all the carriers were destroyed. The aircraft stayed.
Catapults and aircraft cost considerable space and weight, and thus were early candidates for removal in favour of additional anti-aircraft guns. Aurora was completed as a flagship for Rear Admiral (Destroyers), her catapult space taken over for the extra accommodations required. By May 1941 the other three Auroras, the smallest modern cruisers, had had their catapults landed. In other classes, replacements of catapults by anti-aircraft weapons began in 1941. Work was usually done when ships became available for major refits.26
The Fairey Seafox was the smaller counterpart to the Walrus, also designed (to an earlier specification) to land in ocean swells. This one is shown aboard HMS Orion, at a southern US port in 1937. The catapult extensions have been retracted. A Seafox from HMS Ajax spotted successfully during the battle of the River Plate.
An Imperial Conference was scheduled for July 1921. The Admiralty revived Jellicoe’s idea of Dominion-sponsored cruiser construction. It argued that light cruisers were particularly well adapted to Dominion navies because they were ‘the smallest and least expensive vessels in which officers and men can adequately be trained and given general seagoing experience in peace’.27 For this reason the big trade-protection cruisers were initially called ‘colonial cruisers’. There was no attempt to lay out total numbers, possibly because they would have been too frightening. Plans Division pointed out that numbers would be needed above all, so that individual cost should be kept as low as possible (a recurring theme throughout the inter-war period), that the cruisers should burn oil, and that endurance should be 5,500nm at 16kts under war conditions. This was far beyond what existing small cruisers could do.28 Plans Division added the new idea that cruisers already present could exert enormous influence as long as they survived, during the six weeks or two months it would take the main fleet to arrive in the East. As before, both Japan and the United States were listed as potential enemies, but planning clearly concentrated on Japan.29
DGD, Rear Admiral F C Dreyer, had been thinking about what sort of cruisers the Empire needed while he had been Jellicoe’s Chief of Staff less than two years earlier.30 He was struck by the trend towards much larger cruisers. The US Omaha class might be seen as a copy of the ‘E’ class (it was not, having been designed earlier), but after the Armistice the US Navy became interested in 10,000-ton cruisers armed with 8in guns.31 In January 1920 in Washington, the American Admiral Mayo explained to Dreyer that in his opinion nothing smaller could carry enough fuel to be of much use in the Pacific. The General Board, responsible for formulating US Navy programmes, recommended that year that thirty such cruisers, armed with 8in guns, be built over the next three years. The US government was unenthusiastic, and even a scaled-down plan for five cruisers in 1921 failed, but clearly future US light cruisers would be 10,000-tonners. The US Navy was reportedly planning to mount ten 8in guns in the planned ships (which seemed to be too much on that displacement). The Japanese had already announced plans for four cruisers of over 7,000 tons (the Furutakas). No details were known.
Dreyer suggested that former German officers and the French gave some pointers towards the future. To the Germans, their wartime Köln class (about 5,500 tons, eight 5.9in guns, 28.5kts) was too slow and too large for the fleet and too small for foreign service. They violated the cardinal rule that ships of inferior fighting power should be fast enough to escape superior ships. The first requirement for a ‘foreign service’ cruiser stated in 1917 was the ability to keep the sea. Speed should be 25kts for long periods and 26-29kts for short ones, to run down and examine fast merchant ships and to avoid the enemy. Guns should be 6.7in or 7.5in; the proposed armament was eight such guns in twin turrets. Torpedoes were desirable. The ship should be armoured against 6in fire. The original proposal was for 12,000 tons, but the Kaiser considered that too small and recommended 14,000 tons.
According to the Naval Attaché in Paris, Admiral Grasset argued that since the Versailles Treaty limited the Germans (still the main enemy) to 10,000 tons, France should go one better with 10,000 tons and 7in or 8in guns. No such ships had yet been ordered. Dreyer considered the French reasoning vicious, because it would start an upward spiral of cruiser development which would prevent the Royal Navy from building enough such ships (he regretted the Hawkins class, which had started the process). Overall, it was clear that cruisers were tending towards 10,000 tons.
Ideally the Royal Navy would build somewhat smaller ships in larger numbers. The places to cut would be torpedo tubes (not needed in a trade-protection cruiser) and side protection against 6in guns (it would suffice to provide a protective deck of moderate thickness).32 In any case, enough armour to defeat 7.5in or 8in guns would add prohibitive weight. Presumably torpedo tubes could be fitted if the cruiser was needed for fleet work.
The great problem of catapult installation was always the centreline space a rotating catapult required, even if it had retractable extensions. HMS Exeter, shown, solved the problem by using two fixed catapults, angled outward. Their success inspired the developed of the fixed athwartships catapults installed on board Southampton and Fiji class cruisers.
As a gunner, Dreyer advocated the 8in gun because engagements would probably be fought at extreme range, and because effective range depended on the ability to observe the fall of shot. Although a 6in gun could range out to 20,000yds, only the splashes of the larger 7.5in and 8in shells could be spotted reliably at such ranges.33 Recent trials suggested, moreover, that a well-designed enemy light cruiser could not be stopped by 6in fire. Dreyer preferred the 8in gun to the 7.5in because it offered superior penetration and bursting effect for a small increase in weight. He hoped that a power-operated 8in mounting could fire five rounds per gun per minute. Ships would have no secondary LA armament, but should have four 4in HA guns for anti-aircraft and star shell. They would also need automatic weapons to counter torpedo planes and distance-controlled boats, both of which Dreyer claimed the US Navy was developing.34 Two of the multiple pompoms then being proposed by the Naval Anti-Aircraft Committee seemed adequate. Any such ship should carry one or more amphibious aircraft (Dreyer recalled the wartime German raider Wolf, which had one such aircraft). Dreyer envisaged a revolving flying-off platform for an amphibious aircraft and a crane to hoist it in. The aircraft would be used for both reconnaissance and spotting. Since the cruisers would operate mainly in the tropics, they should have improved ventilation arrangements and a magazine cooling plant.
On this basis Dreyer suggested five alternatives:
A: 10,000 tons, 31kts, eight 8in twin splinter-proof on centreline.
B: 8,500 tons, 32kts, five 8in single splinter proof on centreline.
C: 7,500 tons, 35kts, four 8in single splinter-proof on centreline.
D: 7,500 tons, 32kts, four 8in single splinter-proof on centreline.
E: 7,500 tons, 25kts, four 8in single splinter-proof on centreline.
Design A would counter the projected US 10,000-ton cruisers, if British finances permitted (the 7,050-ton Omahas would, however, outrun them). It would not be desirable to go below 7,500 tons, ‘as this is the smallest size now advocated by other countries’. Director of Plans protested that existing Japanese cruisers were much smaller, but for Dreyer the problem was what was coming, not what already existed. No 6in cruiser could effectively fight an 8in cruiser. Dreyer preferred a 7,500-tonner armed with four centreline 8in guns (he was willing to accept 7.5in if DNC could not provide power hoists and power ramming while providing the desired endurance, maximum speed, and other items on the tonnage [i.e. on a limited cost]). The armament decision seemed urgent, if a concrete plan was to be presented to the Imperial Conference. Dreyer particularly cautioned that the Dominion governments should not be misled into imagining that they were being asked for nothing more than the wartime fleet cruisers. However, he also feared that buying cruisers comparable to the largest ones being planned abroad might (as with the Hawkins class) lead other navies to build even larger ships. Hence his preference for the four-gun 7,500-tonner. He also warned that, given his own experience over the last seven years, it might be some years before any Dominion ordered a new light cruiser. He did not make the implication explicit: some or all of those trade protection ships would have to come out of Royal Navy funds. Of the alternatives listed, C to E differed in endurance and protection. Cruiser E was a minimum ship for convoy protection, but she would be unable to attack or run down enemy cruisers. In effect Dreyer had described the next step in cruiser development.
DCNS agreed that any new trade protection light cruisers would have to be armed with (at least) 7.5in guns, and would probably be comparable to the big Hawkins type. He doubted that a ship of smaller displacement could combine sufficient radius of action and armament.
The problem was numbers. In July 1918, when practically all trade between North America and Europe was being convoyed, as well as a proportion of vessels outward bound to North America, and ships operating between Great Britain and Sierra Leone and Dakar, convoys required no fewer than seventy ocean escorts, including cruisers, armed merchant cruisers and commissioned escort ships. A worldwide convoy system would have required about 150 ocean escorts (apart from ASW ships in local escort groups). The most powerful potential Japanese raiders were the four Kongo class battlecruisers, which could be contained only by their British equivalents. For this reason the Royal Navy periodically considered stationing some or all of its battlecruisers in the Far East (a plan to this effect was nearly put into effect in 1929). However, a smaller number of unusually powerful British cruisers working with convoys could make Japanese attacks on convoys too risky. To attack Empire commerce, any Japanese cruisers would have to operate far from their bases; even limited damage might prove fatal (as was the case with the German Admiral Graf Spee in 1939). The wartime ‘large light cruisers’ (Courageous class) might be a useful model for future construction. In the past cruiser size had been held down to make it possible to build such ships in quantity, particularly for fleet operations. However, the fleet might need fewer cruisers if the promise of carrier-borne reconnaissance aircraft was realised. Five Courageous-class cruisers would cost about as much as eight Hawkins.
ACNS suggested (and DCNS agreed) to ask DNC to consider two alternatives. One would be a 33kt 10,000-tonner armed with 7.5in or 8in guns, without torpedo tubes, and otherwise as Dreyer had proposed. Endurance would be 5,500nm at 16kts, and in contrast to the wartime Hawkins, the ship would burn only oil fuel. The second would have much the same characteristics, but with more powerful (preferably 10in) guns, and magazines protected against 8in fire. Maximum displacement would be 15,000 tons. DCNS added that the term Commerce Protection Cruiser should be dropped in favour of some alternative, preferably Station Cruiser – which would recall the much earlier practice of keeping powerful armoured cruisers on the foreign stations, for presence as well as for trade protection. The Dominions should want a ship which could go anywhere and fight anything short of a battlecruiser.
DNC could not produce the desired pair of designs, because his department was fully occupied producing the new battleship and battle-cruiser designs as well as other vital work (including the cruiser-sized minelayer described in the Appendix and the flush-deck carrier conversion of HMS Furious), but he produced some quick estimates.35 His main conclusion was that the Staff had grossly underestimated what was needed to achieve either the desired speed or the desired endurance. For example, using lightweight (‘E’ class) machinery, an enlarged Hawkins (11,000 tons) might make 31kts. To achieve the desired endurance, the ship would have to be lengthened to about 600ft (about 12,000 tons). To make 33kts, she would need about 30 per cent more power (using lightweight machinery, about 12,500 tons). To provide deck space for the amphibian, she would have to concentrate her armament (six rather than seven 7.5in) in three twin turrets; without the amphibian she could probably have another pair of such guns. The proposed 10in ship would probably be about the size of HMS Courageous (19,000 tons).