A World at Arms (76 page)

The other critical element in the great increase in U-Boat successes during 1942 was the introduction by the Germans of a version of the enigma code machine for submarines, effective from February 1, 1942, which added a fourth wheel to that machine and was not broken into by the Allies until mid-December 1942. For most of the year the British struggled unsuccessfully with the new submarine code, called Triton by the Germans and Shark by the British. This not only kept the British from following the directives to and reports from the U-Boats as had often been possible earlier, but it also concealed from them until the end of 1942 that in the same month as they introduced the new fourth wheel, the Germans also completed their reconstruction of the British Naval Cypher 3, the main code used for and by the Allied convoys in the Atlantic. The result was a steady level of very high sinkings during 1942, culminating in November with losses of 721,700 tons, the worst month of World War II.
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Unlike the Poles, who had shared their knowledge of the enigma machine code system with the British in 1939, and the Americans, who had provided them with a machine for reading the Japanese diplomatic “purple” code in January 1941,
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the British most unwisely did not share their work on German codes with the Americans until months after the United States had been drawn into the war.
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Given the technological resources of the United States, this contribution to the shipping disaster of 1942 may well have matched that of the tardiness of the American navy in the first half of the year. In the event, it was the capture of
important cryptographic material taken from a U-Boat sunk in the Eastern Mediterranean on October 30, 1942, that made it possible to begin breaking the new submarine code machine on December 13, 1942.
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In the meantime, the struggle had shifted back to the central North Atlantic with both sides making more efficient use of their respective ships. The Germans had begun in 1941 with the modification of submarines to serve as refuelers for others, and the first of these so-called milch cows, or tanker U-Boats, became available in April 1942. From that time on, these ships played an important role in the Battle of the Atlantic by enabling German submarines, once they had arrived in the central North Atlantic, to extend their stay substantially by refueling at rendezvous with the tankers and sometimes taking aboard additional torpedoes as well.
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Conversely, after months of debate and preparations, the convoys in June 1942 began to include tankers which refuelled the escort ships, thereby greatly facilitating effective use of these vessels, always in short supply.
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In the summer of 1942, the situation in the central North Atlantic was becoming more difficult for the Allies because the number of German submarines at sea was steadily increasing from 22 in January and 16 in May to 86 at the beginning of August and over 100 by October.
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Dönitz enjoyed the full support of Hitler, who considered the V-Boat war as second in importance only to the new offensive Germany was about to begin on the Eastern Front.
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It was to assist the Russians that the Allies ran convoys to the north Russian ports of Murmansk and Archangel; and the German navy and air force, on the other hand, fought hard to keep the weapons and supplies from reaching the Soviet Union by the route the latter preferred because it brought them closest to the front.

It was in this connection that the attack on convoy PQ 17, which left for the Soviet Union on June 27, 1942, and was largely destroyed in the following ten days, combined a great victory for the Germans and defeat for the Allies with a major strain on the alliance of the Western Powers with the Soviet Union. The order of Sir Dudley Pound, the First Sea Lord, to the escorts to withdraw and the convoy to scatter was given, against the advice of his intelligence experts, in the mistaken belief that the
Tirpitz
might have sailed to intercept the convoy. In the ensuing slaughter by planes and submarines, 26 out of the 39 ships in the convoy were lost, taking thousands of vehicles and hundreds of tanks and planes-to say nothing of most of the crews–with them; and, as a result, the British government decided that such convoys ought to be suspended until the winter because the demands of “Torch,” the planned invasion of Northwest Africa, had to have priority.
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This caused a major rift in the Alliance as the Soviet government clamored for aid in its time of great peril in the face
of the German summer offensive, but the shipping and escorts were simply not available. The other side of this coin, however, was that Torch, once successfully launched, forced the Germans to divert torpedo bombers from northern Norway to the Mediterranean. In the meantime, in September 1942, there had already been resumption of convoys to Russia, now for the first time accompanied by an escort carrier.
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PQ 18 saw the ratio of loss reversed, with 27 out of 40 arriving safely; and thereafter, following the two months’ interruption in convoys to Russia necessitated by Torch, the situation steadily improved.
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Nevertheless, the shock of what had happened to PQ 17 remained as a warning of what could easily go wrong and what the implications of such set-backs could be.

The fact that Torch coincided with the month of the heaviest Allied shipping losses can be seen as an illustration of how the shipping problem dominated Allied strategy. One of the major reasons for launching this operation in the first place had been the hope of opening the Mediterranean to ships so that the long and wasteful route around the Cape of Good Hope would not be necessary. We have already seen how the demands of Torch forced an interruption in convoys to Russia in July and August and again in September and October. Furthermore, the shortage of shipping imposed restrictions on the scope of Torch that would, as will be discussed in
Chapter 8
, make it impossible for the Allies to seize Tunisia in the initial stages of that operation. This made it possible for the Germans to hold on in North Africa until May 1943 and hence make an invasion of Northwest Europe impossible before 1944. With shipping losses continuing to exceed new construction, it should come as no surprise that at the January 1943 conference of the Americans and British at Casablanca, top priority should be assigned to the battle against the U-Boats. If this menace could not be conquered, the steady diminution of Allied tonnage would immobilize the Western Allies; even if Britain could be kept supplied, there was nothing a huge American army could do to help defeat Germany if it could not be brought to Europe and supplied there.

At the Casablanca Conference there was a great deal of discussion and disagreement on many issues, but on one there was immediate and general agreement within the American and British delegations and between them.
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The war at sea had to have the highest priority. “Defeat of U-Boat remains a first charge on the resources of the United Nations” was the opening of the agreed memorandum on the decisions reached at Casablanca.
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Two decisions were taken to implement this assertion of priority, one affecting the air forces, and one pertaining to the situation at sea.

The decision about the air forces of Britain and the United States
was to assign the German submarine construction yards the highest priority as targets for the combined bomber offensive, followed by the aircraft industry, transportation, oil plants and other war industry in that order.
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The bombing of submarine pens built by the Germans on the French Atlantic coast and of U-Boat building yards in Germany which followed proved to be an expensive failure; expensive in that in January to May 1943 266 airplanes were lost in almost 7000 sorties; a failure in that no bomb ever penetrated one of the U-Boat pens and no appreciable damage was inflicted on the construction yards.
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Not until 1944–45 could the Allied bombing offensive have an important impact on German submarine construction; in the most critical years of the war, the issue was left to the naval portion of the Allied forces.

The decisions about sea operations concerned the need for continued and accelerated construction of escort vessels, though with the recognition that the “minimum acceptable requirements of escort craft will not be met until about August or September 1943. We ought not to count on the destruction of U-Boats at a rate in excess of the production rate before the end of the year.”
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Since simultaneously the Germans were increasing their construction and commissioning of submarines, the stage was clearly set for the series of great battles which characterized the following months.
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In January and February 1943 the convoys were often successfully routed around the lines of waiting submarines; but delays in reading the German warship code settings for the day, German reading of the British convoy code, and the very number of submarines which often led a convoy safely directed around one line of submarines into the search area of another, brought on a number of the most desperate battles in March. In these engagements many Allied ships were sunk, but the convoy escorts were fighting back hard and often successfully. In the next two months, the slugging match turned slowly but effectively in favor of the Allies. Even when the convoy could not be alerted in time, Allied knowledge of which convoys were in danger and which not enabled them to concentrate escort ships and special task forces of escorts organized into “support groups,” also called “hunter-killer groups,” now including escort carriers, at the danger spots.

The placement of Huff-Duff on all escorts, the increased number of escort vessels, the larger number of very long range planes, and the addition of a “Tracking Room” in Canada to follow and control operations, all helped the embattled convoys. Time and again the U-Boats were driven off with the balance of losses shifting steadily against them: in May the Allies were sinking them at the rate of one per day out of
the over 120 out in the Atlantic. Some of the U-Boat aces, who had run up big scores in early 1942, went down at the same time as more and more of the newly commissioned submarines were sunk on their first combat patro1.
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Signs of reluctance were beginning to be evident in the tactics of some of the submarine commanders, and all the exhortations and complaints of Admiral Dönitz, directing the battles personally and on an hourly basis from headquarters in France, could not reverse the tide which was turning decisively against his ships with a rapidity for which, because of earlier exaggerated claims, he was not prepared. On May 24, 1943, Dönitz acknowledged that the battle had been lost for now, ordered his submarines to move to less dangerous waters further south and looked for new weapons and tactics to return to the northern convoy routes in the future.
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Knowing that control of the seas was essential and that the Germans would certainly try again, the Allies did not relax;
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on the contrary, having earlier determined from their own reading of German signals that their convoy code had been broken, they switched to a new system which helped protect them thereafter.
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The Germans, on the other hand, answered their own repeated queries about the security of
their
codes in the negative and remained confident that no one could penetrate their machine codes, holding to this view not only during World War II but for decades thereafter.
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They believed that Allied radar was primarily responsible for the disastrous losses they had suffered and recognized neither the vulnerability of their codes nor the possibility that the escort ships could locate attacking submarines from their radio messages to other wolf–pack ships.

There was still another element in the changing balance of war at sea. The construction of new ship tonnage had exceeded submarine sinkings for the first time in February 1943, the month after the Casablanca Conference. By September or October it was exceeding the losses due to all causes.
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Thereafter the construction curve continued to rise dramatically even as losses levelled off. Contrary to German expectations, the United States not only built enormous numbers of ships of standardized design more and more quickly; it could man and arm them.
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By the end of the war, 4900 ships totalling 51.4 million tons had been built for the Maritime Commission;
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additional ships were built privately. Simultaneously, the continued commissioning of escort vessels and escort carriers made it possible to protect these increasing numbers of merchant ships and to hunt submarines. Opening the Mediterranean in 1943, furthermore, finally enabled the Allies to utilize shipping more effectively. At last it looked as if the shackling of Allied strategy by the
shortage of shipping might be ending. But the Germans and their Axis partners did not give up that easily.

From the perspective of the Germans, the war against Allied shipping remained central. They had long stressed this point to the Italians and Japanese.
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The Italians had deployed a substantial number of submarines into the Atlantic, and during 1942 and the first months of 1943 had sunk over 350,000 tons of Allied shipping there.
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The collapse of Italian military power with the surrender of Axis forces in Tunisia, however, completely altered this portion of the war at sea. Thereafter the role of the Italian submarines would be increasingly in their use as blockade–breakers by the Germans, an aspect included in the discussion of that topic below. As for the surface ships of the Italian navy, the Germans and even more the Japanese were most anxious that these should not fall into Allied hands as they anticipated Italy’s surrender, a surrender which took place in September 1943. In the converse of British anxiety over the French fleet in 1940, the Japanese now hoped that the Germans could capture or sink the Italian fleet. The Germans’ hopes and plans for seizing the Italian navy succeeded in part and failed in part; they sank the battleship
Roma
and captured or destroyed more ships than Italy had lost to the Allies in the three preceding years of war, but many of the warships slipped out of the Italian ports. Whether they were used again or not, their absence from the Axis side reduced the pressure on the British navy.
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