Out of every hundred boats that put to sea after the crisis of May, 1943, thirty-five might never return. Although the rate of loss showed a slight decline at the beginning of 1944, life in the U-boats had by then become predominantly a struggle for survival against an enemy who ruled both sea and sky. It took from ten to twelve perilous days, creeping slowly through the Bay of Biscay, usually submerged—sometimes for twenty hours on end—before they reached the Atlantic battle zone; and the crews knew that only three or at the most four boats out of every five could expect to return.
The chances of success had steadily decreased since the day when the search-group tactics were abandoned, the wolf packs were dissolved and the boats were sent out singly, each to its own independent area. As long as they had no adequate protection against radar location, their chances of survival must decrease still further.
In January, 1944, a new radar device which operated on a medium wave length had been recovered from a crashed enemy bomber. It was essential to provide a radar detector that could operate on this wave length, and in March the U-boats began to receive an apparatus with the code name of “Midge.” This was only one of a long series of radar search receivers which were produced in the desperate race to keep abreast of new enemy techniques. The series had begun with the Metox or Grandin of unhappy memory, had continued with the “Bug I” and “Bug II,” the Hagenuk, Bor-kum, Naxos, “Fly” and “Midge” to the combined Tunis and Gema. Finally there was the Hohentwiel—a search radar of the kind suggested by Captain Meckel as far back as 1942; this was eventually installed in U-boats in March, 1944.
The struggle was becoming more and more a test of nerves, in which the U-boat men had only their own high morale to make up for the inadequacy of their technical equipment. They could not be sure of a respite even when traveling submerged, for nearly every week the enemy added something new to his nerve-shattering collection of acoustic devices. Apart from the “Foxers,” which emitted their own peculiar sound, there was the pinging and howling of the sonar impulses, tapping blindly round the hull, now fading away, now increasing to menacing strength. There was the “circular saw,” which began with the deep hum of a bumblebee and rose to the thin high-pitched whine of a mosquito, then steadied on a metallic note which jarred the nerves of the men in the depths who, lying in their bunks to conserve oxygen, wondered what new sort of deviltry this noise could signify.
Whenever the boats returned to port, the commanders had new experiences to relate. One of them reported that the enemy was using a new type of noise-making buoy which imitated propeller sounds and sonar impulses. It looked, he said, like a black box with a spike on top and was obviously designed to scare U-boat men. Another reported a new type of explosive locating device, while a third told how he had been attacked by an aircraft using rockets. The enemy’s latest sound gear was clearly much more powerful than the earlier models, for one U-boat had been located at a range of between 10,000 and 15,000 yards; the new and bigger depth charges, too, had damaged one U-boat’s pressure hull at a depth of 650 feet. It was later established that this was the “killer” depth charge, which contained 1,000 pounds of explosive.
The U-boats now used their radio only when absolutely essential or when directly ordered to do so. As a result the U-boat Command, now transferred to a new headquarters code-named Koralle at Bernau near Berlin, received only the briefest reports and was often better informed by the radio intercept service than by its own boats. For the first time since 1939, it was really difficult to form an accurate estimate of the situation at sea; for days on end headquarters would remain ignorant of whether a boat was still “alive,” because she had had no chance of reporting or of answering signals.
The boats were now widely scattered over the Atlantic, for the enemy must be kept aware of their presence, so as to compel him to expend his forces on convoy-escort work. The chances of attacking were becoming rare and since it was vital to conserve their numbers, they were told to avoid operating in areas where enemy patrols were known to be particularly strong. There was good reason for conserving strength at this time. A considerable number of VIIc boats had been dispatched to the Mediterranean since the previous autumn; and since January, 1944, thirty boats had been diverted from the Atlantic for operations against the Murmansk convoys; while from February onward there was growing evidence that the enemy was mounting a large-scale invasion of the Continent, and precautionary measures had to be taken accordingly.
[Between September, 1943, and May, 1944, twenty-three U-boats attempted to enter the Mediterranean; thirteen succeeded, six were lost in the attempt and four abandoned the attempt.]
But where would the enemy land? The U-boat Command ordered a score of boats under Commander Schütze to Norway, as a precaution against a possible invasion of Jutland. When the tension heightened in March, fifteen Type VIIc’s were ordered to stand by in the Biscay ports as the “Landwirt Group,” which was strengthened by all boats arriving from home ports and those which had completed repairs in the Western dockyards.
At about this time the boats began to receive a new type of extensible snort to replace the earlier folding model. The object of fitting this equipment was not to restore the aggressive powers of the existing boats but to increase their chances of survival, and to relieve their feeling of helpless insecurity at sea. The installation of snort in the boats was, however, a slow process, for the overworked yards were no longer capable of meeting these new demands. Due to the bombing of supplies in transit and the growing disruption of communications in France, only about ten of the Atlantic-based boats could be so fitted during the month of May.
The experiences of the early snort boats hardly inspired confidence. The very first, U 264 commanded by Lieutenant Looks, was sunk by a British destroyer in February, and the captain and chief engineer of a second which was also lost had been very critical of the device; although a special snort school was formed at Horten in the Oslo fjord, the commanders still regarded it with the deepest suspicion.
The snort head was fitted with a covering of foam-rubber intended to absorb the enemy radar impulses, and also with a search radar aerial for use while “snorting”; but all in all, there was not much fun in “snorting.” If the snort dipped under in a seaway, the valve closed automatically and at once the diesels would suck all the air out of the boat, the consequent vacuum unpleasantly affecting eyes and ears. If the snort stayed under too long and the water pressure in the air pipe exceeded the pressure of the diesel exhaust gases, these gases were blown back into the boat, where their high content of carbon dioxide brought on every sort of symptom among the crew, from headaches, exhaustion and aching limbs to vomiting and even total collapse. It was Schröteler in U 667 who eventually found the answer; he claimed to have spent nine days submerged on the homeward run without once surfacing. The important thing, he said, was to cut off the diesels immediately when the boat dipped, thus avoiding the danger from the exhaust gases. It was also essential to adjust routine in the boat to the requirements of “snorting”; if this was done, all would be well.
There were still a few boats operating in distant waters, and these accounted for most of the successes that were still attainable. U 66, under her third commander, Seehausen, sank five ships in the Gulf of Guinea. But when three more boats were dispatched to the same patrol area, they found the seas empty of traffic. Since the Allies had opened up the route through the Mediterranean, the alternative way round the Cape of Good Hope had lost much of its importance.
Some startling intelligence was now received which indicated that the enemy was endeavoring to locate submerged U-boats by means of buoys dropped by aircraft, called “Sono buoys.” It appeared that these buoys automatically transmitted the result of their sonar impulse return to the aircraft. Soon after the first report of this device was received, a decrypted signal was picked up from an enemy aircraft in the Caribbean, which reported “sound contact” with a U-boat. This could only have been achieved by an intermediary device such as a sono buoy, as aircraft had no means of directly locating a submerged U-boat. U-boat commanders at once received orders to withdraw at high speed upon locating any such buoys.
No matter how far afield the U-boats ranged, their appearance was soon followed by a reinforcement of the enemy’s A/S forces; there was evidently no area which he could not swiftly cover with a tightly drawn net of patrols. On March 12, Pich in U 168, Junker in U 532 and Lüdden in U 188 were due to rendezvous between Madagascar and Mauritius, to refuel from the tanker Brake. The secret meeting place lay well away from the shipping lanes—yet scarcely had U 188 interrupted her refueling owing to the approach of bad weather, when her lookouts sighted an aircraft followed by a smoke cloud. The U-boat crash-dived and lay for forty long minutes soundlessly in the depths, while faint propeller noises could be heard in the sound gear on the same bearing as the smoke cloud. Then salvos of shells began to fall around the tanker and the U-boat men counted 148 explosions mingled with 14 heavy detonations, some of which shook U 188 herself. For nearly an hour the noise went on, to be followed suddenly by the sounds of cracking and groaning as the Brake sank, and then another half hour of lesser bangs. At last all was still again, and Lüdden came cautiously to the surface. All he could se« was a broad odoriferous streak of oil, a few pieces of floating wreckage, and in the distance the tanker’s boats, heavily laden with survivors. The sun had gone down and night came with tropical swiftness as Lüdden hastened to pick up the survivors; later he handed them over to Pich in U 168.
In April, 1944, three boats bound for West Africa together with U 66 were due to refuel from U 488, the last of the U-tankers; her captain, Studt, had last made a report on March 30, but in those days there was nothing abnormal in a boat remaining silent for three weeks. U 66 was due to refuel on April 26, and Seehausen brought her to the meeting place on the twenty-fifth; finding strong patrols of carrier-borne aircraft, he stayed deep. That night he heard the sudden crash of several depth charges, followed by sinking noises; the next day U 488 failed to appear. U 66 slowly began her homeward run, surfacing for only a few hours at night to charge batteries. Her fuel tanks being almost empty, replenishment was essential. On April 29, Henke in U 515 was sent orders to steer toward U 66 but Henke failed to acknowledge the signal. As was learned later, his boat had been sunk by four destroyers and aircraft from the carrier U.S.S. Guadalcanal, he and some of his crew being taken prisoner. Thereupon Lauzemis in U 68 was ordered to go to U 66; U 68 failed to reply. U 288 was then ordered to the rescue, for U 66’s position was getting desperate. The following night, Lüdden in U 188 heard heavy depth-charging close to the appointed rendevous; the next day he waited in vain for U 66 to appear.
Because of these bitter experiences it was decided to initiate trials in the Baltic with underwater refueling between U-boats.
In the north a few U-boats were beginning to creep in, one at a time, to the English coast. No boat had been seen there for many a long day and their sudden reappearance would, it was hoped, upset the enemy’s calculations. At the same time, four or five weather-reporting boats were stationed to the west of Britain, in the same waters where, a few years previously, the great U-boat “aces” had fought their nightly battles with the convoys. Now the U-boats could barely hold their own against the overwhelming number of hunters.
At the end of May the first snort boats returned to their bases after a week’s patrol in the English Channel. Although they had no sinkings to report, they had at least achieved something which could be reckoned a success; they had proved that they could remain right under the enemy’s nose in the shallow coastal waters—and at the moment that was more important than any victory, for it foreshadowed the possibility of the Wolves being able, with the help of the snort, once again to harry the enemy’s lines of communication.
The sinking figures so far were certainly very disappointing. According to British statistics, thirteen ships totaling 92,000 tons had been sunk in January, eighteen of 93,000 tons in February, twenty-three of 143,000 tons in March, nine of 62,000 tons in April and only four ships of 24,000 tons in May; altogether sixty-seven ships totaling 414,000 tons in all operational areas from the North Cape to the Indian Ocean, from the Bay of Biscay to the Caribbean, as well as a couple of destroyers—an average of thirteen ships, or little over 80,000 tons, per month. That meant that during these five months, only one ship had been sunk every other day; it was painfully clear that the enemy was easily gaining in the race between new construction and losses of merchant ships, whereas the U-boat losses, though less than in the summer of 1943, were still very high.