The first U-boat sinking by the USS Roper came as an enormous relief to the British naval establishment. The figures on merchant shipping sinkings remained grim; in three months Allied shipping losses had totalled 1,200,000 tons, half of which were tankers, but at least there was a 25 percent drop from 500,000 tons in March to 400,000 tons in April. For the third successive month, Doenitz had concentrated his attack on independent shipping in the Western Hemisphere, at the moment mostly in the south. Admiral Andrews’ convoys and the increased anti–U-boat activity provided by the British trawlers helped keep sinkings down along the American coast. Around the middle of the month, Doenitz diverted several boats to an area northwest of Bermuda, and a number of ships were sunk there.
On April 16 Admiral Andrews enjoyed another minor victory: the British finally agreed to open the Halifax convoy cycle from six to seven days, which released two escort groups for use along the West Coast of the United States. Also, the British had sent Captain G.E. Creasy, the Admiralty director of antisubmarine warfare, to Washington to teach the Americans the tricks of the trade. Admiral Harold Stark was appointed to command American naval forces in Europe, and the Admiralty laid out for him a review of their antisubmarine warfare procedures. Belatedly the Americans were taking an interest in what they should have learned two years earlier. But the British gave them full credit for the fifty old destroyers and ten Coast Guard cruisers. Had the Americans retained them, they would have had sixty potential escorts, enough to run four or five convoys.
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One day in April a ship reported sighting a “supply submarine” in the Caribbean area. Admiral Doenitz’s “milch cows,” the tanker submarines, could now enable the U-boats to extend their cruises, and the Type VII boats could now perform as long as the Type IX boats. In April the “milch cows” were moving around the Atlantic, and on April 20 the U-459 arrived off Bermuda and began refueling fourteen U-boats. But even as Doenitz took advantage of his technical superiorities, the ratio of sinkings began to fall. There was no mystery about it: the moment the Americans adopted the convoy system up and down the U.S. coast the sinkings decreased. What was needed now was a convoy system for the Caribbean, but the shortage of escorts prevented that. So in April sinkings in the Caribbean remained high; losses would remain high until the small destroyer escorts began to emerge from the American shipyards.
One other U-boat was sunk that month by Commander Walker’s escort group on the Gibraltar convoy run. There was little submarine activity against Atlantic convoys. The British, Canadians, and Americans had pooled their antisubmarine forces for convoy and now operated under an efficient single command. The British were working on several new antisubmarine devices and had developed the “hedgehog,” a multiple tube launching device to throw depth charges from an escort in a pattern designed to give the maximum coverage of an area. The RDF (sonar) system was improving every month. The Americans were working on a lighter device called “the mousetrap,” which was capable of throwing a group of hedge-hog charges directly ahead of a vessel. The advantage of the mousetrap was that it could be used by a small patrol craft that could not accomodate a Y gun or the hedgehog apparatus.
But as the British well knew, none of these devices could match the escorted convoy. During April, 474 ships arrived in United Kingdom ports in 19 ocean convoys. Only 4 ships were lost, and a fifth from an outward bound convoy. Until the United States could convert its enormous productive capacity into the development of numbers of escorts, the sinkings would continue. But the British remained serene; events were heading in the proper direction.
Captain Creasy stated: “If the early months of 1942 have seen a deterioration in the Battle of the Atlantic the later months of 1941 have seen a steady and progressive improvement and, with the maturing of the plans of the United Nations, this stage will come again. As has been said, we have beaten the U-boats once. We will now beat them a second time.” All one had to do was remember the story of Convoy HG 76. Beset as the British were again, such confidence was remarkable. For in addition to the slaughter on the East Coast of the United States which would continue for weeks to come, Germany’s U-boat production was increasing and Doenitz now had nearly 300 boats available. A new “soft spot” was being worked. Following Hitler’s attack on the USSR in June, Britain and America had begun sending supplies to the Russians, and the supply convoys to Murmansk were now under attack by about 15 U-boats. So far these attacks were not serious: the U-boats were having difficulties with weather and ice. And, the British noticed that the quality of the crews sent to the north was not as high as that of those in the Atlantic. But that would change as the new men gained experience.
Doenitz was indefatigable in searching for that “weak spot” in the Allied defenses. In May, with still more boats at his disposal, he renewed his assault on the Atlantic convoys, while not neglecting the American area. Despite bad winter conditions in the north, he sent a boat to the Gulf of Saint Lawrence, which sank two ships. The Canadians responded with intensive air and sea antisubmarine measures and added escorts to every convoy no matter how small. The sinkings ceased.
The U-boat operations in the Atlantic in the spring of 1942 took a different turn, as the attack on Convoy SL 109 indicated. Doenitz was looking for soft spots again and thought he had found one off the bulge of Africa, where the Freetown convoys moved.
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The thirty-one-ship convoy was under the protection of the Fortieth Escort Group consisting of four escorts with the destroyer Landguard in command. The convoy was steaming north at 7.5 knots on the afternoon of May 11 when the escort Lulworth sighted a suspicious object almost dead ahead on the horizon. Three escorts hurried to check the object which was identified as the conning tower of a submarine. The U-boat was steering across the course of the convoy from port to starboard, apparently planning to move down the starboard side to attack. The convoy made an emergency turn to port and the escort Bideford took station on the starboard beam.
Meanwhile, the U-boat had made a high frequency radio transmission and then dived. The transmission was picked up by the Bideford and by a second escort, the Landguard; the triangulation gave them the point where the U-boat had dived. Two escorts then set out to sweep and drop depth charges. Unfortunately the charges knocked out the asdic set of the Landguard.
At 5:50 P.M. the escort Hastings obtained an asdic contact two miles from the U-boat’s diving position. Three of the escorts attacked with depth charges. Three hours later another contact resulted in another depth charge. No signs of damage were apparent, but the area had a strong smell of oil. The escorts then rejoined the convoy, arriving on station at 3 A.M. No more signals were intercepted, and no other U-boat was sighted that night.
At 3:30 P.M. on May 12, the lookouts of the Hastings sighted a submarine ten miles west of the convoy. Two escorts gave chase, but the U-boat scurried off at high speed on the surface. At 5:30 P.M. another U-boat was sighted twelve miles ahead of the convoy and the escorts went after this one. A cat and mouse game began. The U-boat turned away, but after one escort started back toward the convoy, the U-boat followed. The captain of the escort knew that the U-boat was going to try to follow him to the convoy, so he slowed down and tried to lure it toward the other escort. The U-boat captain was as canny as the destroyer captain, and the ruse failed. The U-boat dived and disappeared. The destroyer altered course to the north, away from the convoy, fired star shells, left a delayed action depth charge as a booby trap, and then altered course in the dark to rejoin the convoy.
While three of the four escorts were out chasing submarines, a U-boat torpedoed the freighter Denpark on the port wing of the convoy. She carried a cargo of manganese ore and sank without time to fire a rocket or send a message. It was ten minutes before another ship could fire a rocket; in the meantime the U-128 had fired on another ship and missed. The convoy now made snowflake to illuminate the area and the escorts moved around searching for the submarine. At 11 P.M. the Landguard made contact with a U-boat 3,500 yards out on the port beam. The U-boat had just surfaced, and the RDF contact was immediately followed by sighting. The destroyer captain set his course to ram and fired snowflake over the U-boat, which blinded the U-boat captain and prevented him from firing on the convoy. The U-boat was too close to fire on with the five-inch gun, but the pompoms and machine guns were turned on it and hits were scored. The U-boat dived and the escort dropped a pattern of depth charges, set shallow, into the swirl. Then contact was lost. Nothing more was heard from the U-boat that night.
Early the following morning, the lookout in the masthead of the Landguard sighted a U-boat 10 miles off the starboard bow. The escort Lulworth was sent to chase. A high frequency transmission was intercepted by escorts, the U-boat dived, and the Hastings was sent to the spot and ordered to keep the U-boat down. The escort began dropping depth charges, even though there was no contact. But the technique was new: the convoy was steering north, so Hastings steered northeast, dropping five single charges set at 150 feet at five-minute intervals. The idea was to suggest that the convoy was steering forty degrees at eight knots. Having done that the Hastings rejoined the convoy.
In the afternoon the Landguard sighted a U-boat again on the port bow at a range of twelve miles. The convoy altered course, thirty degrees to starboard. But the Landguard did not try to chase. Her captain reported:
At this stage it was considered that no good results could be obtained by attempting to chase this U-boat as there was every indication that there were several in the vicinity of the convoy and the experience of the previous night proved the importance of the escorts remaining with the convoy.
The convoy commander considered the possibility that the U-boat was shadowing the convoy because of the smoke coming from several ships. When the convoy altered course, the Landguard stayed on the old course and made smoke to lure the U-boat. But it did not work. The transmission was heard again, off the convoy, indicating that the U-boat was shadowing. The Landguard speeded up and rejoined, following an evasive course to throw off any other U-boats in the vicinity. She was back on station on the bow of the convoy by dusk. At 8:40 P.M. the convoy altered course to starboard. Fifteen minutes later the steamer Ingria sighted a U-boat on her port bow and fired snowflake. The convoy followed suit and the area was lit up like a football field on a Saturday night. The commodore’s ship, the Thomas Holt, fired its Oerlikon guns at the U-boat and changed course to ram. With the Oerlikon tracers coming at it, a ship turning to ram, and the night as light as noon, the U-boat captain lost heart and beat a retreat without firing a torpedo. The Lulworth, on the other side of the convoy, came around and chased the U-boat. The U-boat dived and four minutes later the Lulworth had an RDF contact; she moved in and began dropping depth charges. The Lulworth then ran out 1,000 yards and reduced speed to twelve knots. The noise of the U-boat blowing its tanks was heard on the port bow and the course was altered. But no further contact was made and the Lulworth rejoined the convoy after midnight.
The Bideford remained and obtained a firm asdic contact on the submarine after the Lulworth left the scene, and dropped a ten-charge pattern. A few minutes later she fired snowflake and saw large air bubbles breaking the surface. They may have been pillenwerfer, which the Germans were now using regularly. No further contact was made, and the Bideford rejoined the convoy, which altered course to fifty degrees.
At 11:10 P.M. the hydrophone operators of Landguard heard torpedo noises, bearing 120 degrees. The ship altered course and went to full speed. The torpedo passed down the side 400 yards away. The area was illuminated but nothing was seen and no U-boat contact was made. It seemed evident that the U-boat had fired from a long distance, by periscope bearing.
At 11:40 P.M. the Landguard intercepted high frequency transmissions and obtained a fix ten miles astern of the convoy. The Bideford was sent back, but did not make contact. Huffduff bearings continued to indicate that the convoy was being shadowed, but the escorts had neither sightings nor any RDF or radar contacts. Nor did any asdic sounds disturb the tranquility of the convoy.
On May 14 the Fortieth Escort Group was weary. The escorts were reduced to 5 percent of their depth charges and the ships were short of fuel. On May 18 the Thirty-seventh Escort Group showed up, and the Fortieth Group then set course for Gibraltar to replenish. The Thirty-Seventh Group had no further difficulty and the convoy arrived on schedule with only one loss, although analysis later indicated the group had been in contact with at least five different submarines during the voyage.
Here was the lesson Captain Creasy was to teach the Americans: antisubmarine patrols were comparative failures, aircraft could be of enormous use in convoy protection, the convoy escorts must be properly trained and known to one another, and RDF (sonar) was enormously valuable.
As regards the comparative failure of antisubmarine hunting forces, this is one of the hardest of all the lessons of the war to swallow. To go to sea to hunt down and destroy the enemy makes a strong appeal to every naval officer. It gives a sense of the initiative and of the offensive that is lacking in the more humdrum business of convoy protection. But in this U-boat war of 1942 fought out in the oceans the limitations of antisubmarine hunting forces have made themselves very clear. . . . Where the position of the U-boat is accurately known and a number of antisubmarine craft are available in the immediate vicinity there is some small chance of locating the enemy. Even in these conditions, the difficulties of locating a U-boat intent on evasion are apt to be forgotten. It is mathematically calculable that four destroyers aware of the position of a U-boat only twenty miles distant have a 40 percent chance of gaining asdic contact.
The performance of the Fortieth Escort Group had certainly shown all these lessons learned. Trailed by five submarines for nearly a week, the escorts had concentrated on the essential but unglamorous job of guarding the convoy day and night. Only when three of the four had gone haring off on submarine chases was a single ship torpedoed. Not a single submarine was claimed as sunk, and there were no heroics involved. But the Fortieth Escort Group had done the job and—on the basis of past performance of the U-boat packs—saved at least a dozen ships from destruction.