When all the German warships had returned to their bases, the Germans as well as the British used the respite to evaluate the lessons from Operation Berlin. Both sides were well informed about the activities of their own ships, but knowledge about the enemy, his means and his measures, was fragmentary. Nevertheless, a few conclusions seemed clear enough. One example was the passage of German ships back and forth from the bases on the continent to the Atlantic. The Admiral Hipper as well as the Admiral Scheer had been able to pass through the Denmark Strait fairly easily on their way from Germany and back to Germany. Admittedly, the Scharnhorst and Gneisenau had run into trouble south of Iceland, but they had subsequently passed through the Denmark Strait without trouble. Thus, it seemed that the Denmark Strait was favourable for break-out attempts. Also from the German perspective, the bases on the French Atlantic coast seemed suitable for cruiser warfare. The Admiral Hipper had twice put into Brest, and subsequently left the port, without being found or harassed by British forces. The Gneisenau and Scharnhorst had also been able to reach Brest, although they had been sighted by British reconnaissance aircraft. It should be remembered that all these operations had taken place during the winter, with longer nights and more periods of weather with limited visibility. During the summer months it might prove more difficult to avoid detection.
But if the Germans had met with few difficulties when attempting to reach the vast expanses of the Atlantic, they had been markedly less successful in their attempts to find convoys to attack. It seems reasonable to assume that these two observations were in response to the simple fact that the oceans were vast, while the ships available were quite few. With this in mind, the advantages of the convoy system practised by the British also become clear. Since it was almost as easy to find a single ship as a convoy, it was better to gather a large number of ships before sailing. If the Allies had chosen to let the merchant ships sail singly, the likelihood of their detection would have been greater.
However, the main advantage with the convoy system was that the warships available for protection could be concentrated in one area, allowing them to act more effectively. The Germans could not concentrate their submarines and surface ships correspondingly, because they needed to disperse their available vessels in order to find a convoy in the first place. On all three occasions when Lütjens had found convoys, a British battleship had been in the vicinity. What the Germans could not know was if it was a regular British procedure to let a battleship escort convoys, or if they did so only when intelligence suggested that German battleships were at sea. As both the Admiral Hipper and Admiral Scheer had encountered convoys not protected by battleships, the Royal Navy probably did not allocate a battleship for each convoy. The German naval staff concuded that it was of the utmost importance to continue to maintain secrecy with regard to both future break outs and ensuing operations.
Lütjens lamented the shortage of reconnaissance aircraft available to him during Operation Berlin. He wanted a hangar, similar to Scharnhorst’s, to be fitted on the Gneisenau, enabling her to bring more aircraft during operations on the Atlantic. Between them, the Scharnhorst and Gneisenau could carry only four aircraft of the type Arado Ar 196, so the loss of even a single machine meant a serious reduction in their capacity to reconnoitre effectively from the air.113
A problem as grave as the limited number of reconnaissance aircraft was the lack of direct communication between surface forces and submarines, caused by different radio frequencies, code systems, call signs and the dependance upon on-shore commanders to forward messages. Although the submarines were often submerged and unable to intercept any wireless signals, most of the time they were at the surface. With effective communications, the surface forces and the submarines would have been able to coordinate their efforts much better. If the fleet commander could take command over a number of submarines when a battle situation arose, it would be possible to co-ordinate combat efforts as well as reconnaissance.114
One of Lütjens’ basic operating principles during Operation Berlin had been to minimize risks to his squadron. He followed this principle in forthcoming operations too. Although additional ships were expected to participate, including more powerful vessels than the Gneisenau and Scharnhorst, it would be wrong to allow the ships to face unnecessary dangers. The main goal of cruiser warfare was to disrupt British trade, which was best accomplished by attacking and sinking British merchant ships. Besides the decimation of the British merchant fleet, the Germans hoped that the cruiser warfare would have collateral effects. For example, if the British were compelled to provide stronger escort for their convoys, more time would be lost while the merchant ships waited before all involved vessels had assembled, thus reducing the transport capacity of the overall system. For these reasons it remained necessary for the Germans to retain their ships as serviceable units, to be able to spend as much time as possible threatening the British shipping lanes on the Atlantic. Since the war began, only the Admiral Graf Spee had been lost in the cruiser warfare on the Atlantic.
An open question was the consequence of including the Bismarck in the projected operation. Her size and firepower increased the range of options available to naval planners. On 2 April, 1941, the German naval staff issued a directive that discussed various ideas with regard to future operations. When both the Bismarck and Tirpitz were committed, it woul be feasible for them to engage the convoy escort, sink it and then deal with the convoy.115 However, while waiting for both these ships to become fully operational, ambitions had to be scaled down. The alternative chosen was to let the Bismarck tie down the escort while lighter ships attacked the merchant ships. Already at this stage it was clear that the heavy cruiser Prinz Eugen would accompany the Bismarck. The Gnesienau would also take part in the operation. She would put to sea from Brest and join the other two ships on the Atlantic. The Scharnhorst could not participate this time because the work on her machines would not be completed in time. It was decided to launch the operation, which was code named Rheinübung, on 26 April, at the time of the new moon.116
Although the directive of 2 April clearly stated that the Bismarck was to attract and tie down the escort, no specific instructions were given as to how she would achieve this end. It was not easy for any ship to tie down an opponent at sea, and to do so without taking risks seemed impossible. It might be possible for the Bismarck to depend on her superior firing range, but this was questionable. To score hits at ranges above 25 kilometres was very rare and only the oldest British battleships had a range of less than 25 kilometres. If the Bismarck had a range advantage, it was rather a matter of probability: she was more likely to score hits at long range, around 20 kilometres or more, but she was far from guaranteed to score the first hit. Another possibility was that the Bismarck could approach the convoy from one direction, while lighter German warships, such as the cruiser Prinz Eugen, remained hidden. If the Bismarck could induce a British battleship to position itself between the convoy and herself, an opportunity might be created for the Prinz Eugen or the Gneisenau to attack the convoy from another direction. This option was also discussed by Lütjens in his directives for the forthcoming operation.117 A close reading of the directive of 2 April reveals that, as with Operation Berlin, the main objective was to sink British merchant ships. Enemy warships should only be engaged if needed to accomplish the main goal and only if it did not involve considerable risk.118
There were no heated discussions about the choice of commander for Operation, Lütjens was chosen without much hesitation, since the instructions he received during the final phase of Operation Berlin had clearly appointed him as commander of Operation Rheinübung too. Lütjens was probably pleased to be confirmed as commander but he soon realized that in one respect it would be a more complicated operation. Unlike the Scharnhorst and Gneisenau, which were virtually identical, the Bismarck and the Prinz Eugen were a rather ill-matched pair. Their battle capabilities were quite different, but assigning different roles to each ship should minimise the disparity. The moderate endurance of the Prinz Eugen was a greater concern, as she would have to bunker fuel much more often than either the Bismarck or the Gneisenau.119 Since it remained vital for the German warships to be able to bunker oil and replenish stores at sea, eight ships were detailed for this important task.120 Still the Prinz Eugen would not be able to sail as far from the supply ships as the other members of the squadron, therefore limiting the range of Lütjens’ actions.
A few days after the directive was issued, events occurred that threatened to upset the plans. On 4 April, the German naval staff had emphasized the need for protecting the warships in Brest from torpedo attacks. For the moment, three battleships could be given adequate torpedo protection and another two could be placed in dock. From June onwards, another battleship could be harboured safely.121 This was deemed sufficient to counter the threat from British torpedo aircraft, but during the night of 4 April, the Royal Air Force directed a bomber force against Brest. No significant damage was caused, but a dud fell in the dock where the Gneisenau was located. To remove the unexploded bomb, the battleship was moved out of the dock and the rough sea thwarted German attempts to place torpedo nets around her. At dawn on 6 April, the Royal Air Force took advantage of the opportunity and launched a surprise attack. It was a tough enterprise, but the British were favoured by haze, which made it difficult for the German Flak gunners to observe the approaching aircraft. The Canadian pilot Kenneth Campbell acted with unusual personal courage. The German fire was very intense and numerous shells exploded around his Beaufort aircraft, but he steadily held his course, a mere 15 metres above the sea. The Gneisenau loomed ever larger in front of him and at extremely short distance, he released the torpedo. Just as his plane felt lighter after losing the weight of the torpedo, it was hit and crashed on the surface of the sea. Campbell never saw how the torpedo hit the stern of the Gneisenau. For his sacrifice, Campbell was posthumously awarded the Victoria Cross.122
The damage caused to the Gneisenau was by no means critical, but it was sufficient to require at least ten weeks of work before she was fully operational, a major setback to German plans for Operation Rheinübung.123
As the spring of 1941 unfolded, more issues arose to delay the planned operation, and even to raise questions with regard to the whole concept of cruiser warfare. One of the most important was the suspicion that the British might have developed radar equipment for use on warships. In April 1941, the German naval staff asked Captain Kranke, who had commanded the Admiral Scheer during its long voyage if he had seen any evidence suggesting that British ships were fitted with radar. Kranke had seen nothing to justify the suspicion, but still it was suspected that the British cruiser Naiad might have used radar when the Gneisenau and Scharnhorst tried to pass between the Faeroes and Iceland on 28 February.124
However, lacking direct evidence to the contrary, for the time being the Germans assumed that British ships were not fitted with radar. As a precaution, a radar warning device was fitted to the Bismarck, perhaps the first ever to be mounted on a warship. However, it only operated within a rather narrow wavelength band and could not detect all types of radar.125
The radar equipment available in the early 1940s was at an early stage of development. It was not capable of precise fire direction and as long as visibility remained good, the human eye was still the most effective way of locking in on a target, since it could more accurately determine ship type, course, range and so on. On the other hand, radar was very useful as a detecting device when visibility was poor, although poor weather such as snow squalls could interfere with its efficiency. Radar could also provide fairly good information on the range and bearing of enemy ships, at least sufficient to inform tactical decisions, although not to direct fire as well as the optical instruments could do.
Nevertheless, it was clear that it was only a matter of time before radar had reached such a maturity that it could ‘see’ ships at long ranges, and any breakthrough in this field would have serious consequences for naval operations that depended to a large extent on the enemy remaining unaware of hostile forces in their area. German naval planners were understandably nervous at the thought that the British were employing a technology that would severely limit, if not entirely preclude, their cruiser warfare operations.
A further factor that gave rise to misgivings about the ongoing viability of cruiser warfare was the condition of the German ships when they returned from operations. As we have seen, after two months at sea, at least ten weeks were required to put the Scharnhorst back into serviceable order. This was not the end of the problems. On 9 April, it was reported that the Admiral Scheer would not be operational until mid-June. Admittedly, she had spent more than five months on operations, but it must also be considered that she had been in the shipyard for repairs during the first year of the war. The Admiral Hipper had put to sea at the end of November 1940, but after a mere four weeks she arrived at Brest for repairs. She would again arrive at Brest, before returning to Germany.126 As the German ships spent so much time in shipyards while mechanical defects were repaired, the time available for operations on the Atlantic was seriously reduced. The German Navy had a very limited number of ships, so to have two or three in the shipyard at a time rendered continued operations impossible.
Furthermore, as shown by Campbell’s attack on the Gneisenau, the German ships were not only menaced at sea, they could also be attacked while in the harbour or shipyard. The Royal Air Force did not hesitate to intensify its attacks on Brest, once the German battleships had arrived. The western French port became a primary target for Bomber Command. On the night of 6 April, a major attack was made, but no damage to the German military installations occurred. The British did not give in. A major attack was again launched on the night of 10 April. This time the Gneisenau was hit by four more bombs, causing fires and casualties. The damage to the battleship was limited, but the event nevertheless caused consternation among the Germans.127
When the German army occupied the French Atlantic coast, the German Navy rejoiced. At last suitable naval bases were available. The distance from the French ports to the convoy routes on the Atlantic was much shorter than the distance from ports in Germany. Furthermore, British countermeasures had been developed on the premise that German ships would pass through the North Sea on their way to the Atlantic. It had been an advantage for the German Navy to occupy bases in Norway, but the French ports were even better situated. The Admiral Hipper had twice used Brest unopposed and the Gneisenau and Scharnhorst had been able to put into Brest without being troubled, although an aircraft from a British carrier had in fact observed them shortly before reaching Brest. Unlike the Norwegian ports, there were ample shipyard and docking facilities in Brest and St. Nazaire. Maintenance and repairs could be performed to an extent not possible in Norway. Unfortunately, in April 1941 it became clear that British air power posed a threat to these plans.
Within the German Navy, opinions on how to handle the threat from the Royal Air Force were far from unanimous. There were several alternatives. The most drastic was to cease using the French ports as bases for major surface warships.128 Instead the big ships would be withdrawn to German ports and would only use the French ports briefly. Rear-Admiral Fricke argued in favour of this alternative.129 He emphasized the short distance between Brest and British air fields. It enabled aircraft to carry larger payloads and even allowed the use of single-engine aircraft. Also, enemy aircraft could make more frequent attacks. Another aspect was the prevalence of agents in French ports, as the resistance movement in occupied areas was a useful source of information to the British. Finally, it was easier for the Royal Air Force to reach Brest undetected. Thus, Fricke argued that the German ships should be transferred to Germany as soon as possible.130
However, it was Admiral Raeder who settled the issue and he wanted to keep the Gneisenau and Scharnhorst in Brest. For the moment, neither battleship was serviceable enough to put to sea. However, Raeder did not want the Bismarck or Prinz Eugen to be stationed in Brest. They would only put into Brest if no major repairs were needed, or to bunker fuel oil or take on provisions and put to sea again. In further support of the continued use of the harbour at Brest, some officers argued that the British attacks on the Gneisenau had been accompanied by a good deal of luck and similar random hits could occur in German harbours, like Kiel or Wilhelmshaven, too.131
One underlying problem was the fact that the Royal Air Force had begun to challenge German air superiority. British aircraft production had increased since 1939 and the effects were beginning to tell. In fact, as the Luftwaffe was beginning to prepare for operations in Eastern Europe, it seemed quite likely that the threat from British air power would become evern more serious in the future.
The Germans made efforts to improve the safety of their ships in Brest. Unsurprisingly, the Flak defences were strengthened and barrage balloons were added. The ships were kept at higher alert, to enable their anti-aircraft artillery to participate in the defence of the harbour. Also, the Germans installed devices that could create artificial fog over the area and the fire prevention was improved. There was a suggestion that the decks and vital parts of the harbour, such as locks, should be reinforced with extra armour plates. To limit the effectiveness of a potential attack, the ships themselves were dispersed, with some destroyers sent to other ports.132
No more damage was inflicted on the warships during the following months so it appears that these countermeasures were effective. However, Bomber Command also directed attacks on the German ports. On the night of 9 April, the RAF attacked Emden, on the German North Sea coast. The bombers mainly carried incendiary bombs and no damage to military facilities occurred. Kiel was also attacked the same night, but again no militarily significant damage was caused. The city itself was more badly hit.133
In any case, the Germans were becoming more reluctant to use harbours close to British airfields. Already on 10 April, they decided that the Bismarck and Prinz Eugen should only put into Brest if moorings well protected from torpedo attacks could be arranged. If not, it would be better for them to set course for Trondheim when the operation on the Atlantic came to an end, despite the disadvantage of once more being forced to break out through the waters around Iceland.134
Unfortunately, Trondheim lacked the facilities needed to carry out substantial repairs. Hitler wanted a large dry dock to be constructed at Trondheim and ordered an investigation into the idea. If possible, it was to be built by Organisation Todt, an organization employing forced labour. Another plan he entertained was to use the Spanish naval base El Ferrol. He intended to occupy it during the autumn of 1941. As usual, Hitler had plenty of ideas, but they were not always easy to carry out. Neither of these projects ever came to fruition.135
The events of early April 1941 called for some reassessment of the plans for Operation Rheinübung. In retrospect, it might have been wiser to postpone the operation until more ships could participate, or even to shelve it entirely. Both the Scharnhorst and Gneisenau were expected to be fully operational by the summer of 1941, and the Bismarck’s sister ship, the Tirpitz, was in the process of shaping up and training her crew. She too would become fully operational during the summer. An operation that employed these three battleships, plus the Bismarck and the Prinz Eugen, could offer a far more serious threat to the British, compared with that of the curtailed version of Operation Rheinübung that remained on the German naval staff’s agenda.
However, there were also factors in favour of continuing with Operation Rheinübung, even without its ideal complement of ships. The British Navy continued to grow, as newly produced ships were commissioned and damaged vessels returned from repairs at shipyards. It was also crucial to consider the role America played. The German Naval Staff was convinced that the United States regarded Germany as a future enemy and that the American position would only become more and more hostile as time passed. If Germany became embroiled in a war with the United States, without Japan declaring war in the Far East, the Allied dominance at sea would become overwhelming. These arguments strongly suggested a prompt staging of Operation Rheinübung.
Hitler’s plans to attack the Soviet Union in Operation Barbarossa also pushed Raeder towards launching Operation Rheinübung as soon as possible. In Germany, the army had traditionally been the dominating branch of the armed forces, while the Navy played the role of the younger brother. When the Luftwaffe was created, the Navy was pushed down one step further on the ladder.
With the onset of World War II, matters changed, as Raeder saw it. Except for the conquest of Norway, the German victories were mainly won by the army, However, according to the German Naval Staff, by 1941 Germany had already defeated its main land adversaries. The remaining enemy, Great Britain, was a sea power and not assailable by the German army. A maritime strategy was required to defeat her. Accordingly, Raeder demanded that the Army and the Air Force should adapt, to allow as forceful as possible a conduct of cruiser warfare against Britain’s maritime trade.
Reichsmarschall Hermann Göring, head of the Luftwaffe, was strongly opposed to Raeder’s suggestions. He believed the Luftwaffe alone could subdue the British and did not want to divert resources to targets deemed appropriate by Raeder, such as harbours and shipping. Göring pursued his own ambitions, which resulted in the Battle of Britain during the summer and autumn of 1940. However, as the Luftwaffe failed, British resistance increased.
By the autumn of 1940, when it became clear that the Luftwaffe had lost the Battle of Britain, Raeder argued more strongly for an expanded cruiser war over the next few months. The Luftwaffe obviously could not defeat Britain alone and the failed attempt had spoiled any chances of reaching a political solution. Great Britain, with Churchill at the helm, was prepared to fight until Germany was defeated. According to Raeder, further bombing would only serve to stiffen the British determination to continue the war. Attacking her maritime trade remained one of very few methods to defeat Britain. However, Raeder realized that once the attack on the Soviet Union was launched, his plans would take second place. He needed a significant success before Operation Barbarossa started, to reinforce his arguments for more resources for his Navy, or to convince the Luftwaffe to direct efforts against British maritime trade.
A basic tenet of the cruiser war concept held that German warships could operate either singly or in small groups. From this perspective, the combination of the Bismarck and Prinz Eugen was equivalent to that of the Scharnhorst and Gneisenau had been. The hypothetical constellation of the Bismarck, Prinz Eugen and several more ships was regarded as being exceptionally strong but since Lütjens policy of avoiding confrontation with British warships had so far allowed the Germans to avoid taking losses in their Atlantic operations, there seemed to be no reason why the risks involved in Operation Rheinübung would be greater. Thus, the ships would be ready to sail from Gdynia on 28 April.136
If Raeder was convinced that the plan should go ahead, Lütjens still had misgivings. Perhaps they were reinforced when Operation Rheinübung suffered yet another setback on 23 April. A magnetic mine detonated about 30 metres from the Prinz Eugen, when she sailed through the strait between Puttgarden and Rödby. The damage caused was slight, but would nevertheless require 12 days to repair. Still, Raeder did not dismiss the idea of sending the Bismarck on Operation Rheinübung alone.
On 26 April, Lütjens again discussed Operation Rheinübung with Raeder and emphasized the need to wait at least for the Prinz Eugen to become serviceable. He also considered it more prudent to wait until the Tirpitz was ready for action, or until at least one of the battleships in Brest could participate. If he only had the Bismarck and the Prinz Eugen at his disposal, he would not be able to use his ships in a way that differed significantly from Operation Berlin. If the enemy offered dogged resistance, and the Bismarck destroyed the escort to allow the Prinz Eugen to have a free hand with the convoy, some kind of damage was almost bound to occur to his battleship. Further operations would then be prevented until the damage was repaired.137
By and large, Raeder agreed with Lütjens. But still, there was the issue of Operation Barbarossa and the possible future involvement of the United States.138 Nevertheless, he agreed to postpone Operation Rheinübung at least until the Prinz Eugen was again combat ready.139
While waiting for new orders from Raeder, Lütjens continued to work out more detailed plans for Operation Rheinübung. The most important issues were the break-out and guidelines for combat. Compared to Operation Berlin, the forthcoming operation suffered from a serious disadvantage. The more the spring progressed, the shorter the nights grew, and Iceland was so far north that the nights would not become dark in June at all. This factor may well have weighed heavily for Raeder when he pushed for an early staging of Operation Rheinübung.140
In addition to the light, weather also prominently affected the chances of a successful break-out. During the autumn of 1940 and afterwards, the Germans strived to take advantage of the new moon when passing through straits like the Great Belt and the Denmark Strait at night. As spring nights became progressively shorter and lighter so that much of the ship movement would take place in daylight anyway, the weather began to play a more prominent role in the choice of time for the operation. This factor also suggested an early launching of Operation Rheinübung, as the kind of weather propitious to a successful break-out was less likely to occur during the summer months.141
It is understandable that the Germans studied the break-out with considerable thoroughness. The gravest threat to Operation Rheinübung was early discovery by the enemy. There were several occasions when the risks of discovery would be heightened. The first was the departure from Gdynia, where the British might become informed when the ships sailed. Once in the Baltic, there was hardly any risk of being detected, but when entering and passing through the Danish belts, the risk increased. On the Kattegat, Swedish ships might observe the German squadron. Furthermore, British submarines and aircraft patrolled the Kattegat and the Skagerrak. Along the Norwegian coast, local people, many of them members of the resistance, might catch sight of the ships. Not until the squadron had reached the Norwegian Sea did the dangers of discovery decrease again.
In the main, the dangers to the secrecy of Operation Rheinübung could be divided into three main categories: British military forces, other ships at sea and observers ashore. Of these, the first category was considered the most serious, as military units could be expected to make a more correct observation and to transmit it immediately. Neutral ships too could be expected to report by wireless that German ships had been observed, but that was not certain. Agents ashore and resistance members could not be expected to report immediately, as they often had to move their wireless equipment somewhere where they felt safe. In the latter case, the Germans estimated that there would be a delay of about 24 hours.142
They were hardly likely to completely avoid detection. Some of the sources used by the British would probably provide them with some kind of information. The Germans relied on two circumstances: that the information might reach the British after some delay and that it might be mixed with other information, true or false, which reached them. Thus it would be difficult for them to judge the German intentions. In fact, the German assumption was fully justified. The British had numerous times falsely believed the Germans were on their way towards the Atlantic. Furthermore, many reasons, other than a break-out, could motivate German ships to sail from Gdynia or pass through the Danish Belts.
An alternative discussed by the Germans was to use the Kiel-canal, rather than the Danish Belts. If the canal was chosen, Lütjens’ squadron could subsequently sail on the North Sea, rather than the Belts, Kattegat and Skagerrak. However, there was a distinct disadvantage with the alternative, as the Bismarck could not pass the canal fully loaded. If she went through the canal, she would have to bunker in some North Sea port before embarking on Operation Rheinübung. The battleship would be forced to spend considerable time in port, subjecting her to the risk of being detected by British aerial reconnaissance. If so, the British would intensify their efforts to discover when she left harbour. At worst, the Bismarck might even be damaged by air attack.143 Compared to these risks, the passage through the Danish Belts appeared to be the lesser of two evils. As the ice had also melted, the Great Belt could be passed in darkness, which would improve chances of avoiding detection.
According to the orders Lütjens issued for Operation Rheinübung, the ships would enter the Korsfiord near Bergen on the fourth day of the operation. Fuel oil would be bunkered. It was especially important to the Prinz Eugen, whose radius of action was much smaller than the Bismarck’s. So far Lütjens’ plans were quite clear. How the next phase was to be conducted was left open. He had almost the same general alternatives as during Operation Berlin. His squadron could set course for the tanker Weissenburg in the Arctic Ocean and bunker fuel oil before breakout. Also, the ships might try to break out immediately, either north or south of Iceland. Lütjens chose to wait before the final decision. However, in his operations order, he declared his intention to bunker from the Weissenburg, after the short pause in Bergen, although he remained open to other alternatives if the situation demanded a change in the plans.144