Hitler launched Operation Marita, the rescue of the Italian armies in Greece, on April 6. Attacking from Austria, Hungary, Romania, and Bulgaria, German ground and air forces simultaneously overran Yugoslavia and attacked the northeastern Greek frontier. Within three weeks, the Germans conquered most of the Hellenic Peninsula, forcing the recently arrived British ground and air forces to evacuate to the island of Crete and to North Africa, where Rommel’s modest Afrika Korps had pushed the Army of the Nile, renamed the British Eighth Army, back into Egypt.
The U-boat war in the Atlantic proceeded in conformity to Dönitz’s decision to withdraw from the Northwest Approaches. On April 1 he shifted the nine boats in the hunting ground very far to the west. They formed a north-south patrol line at 30 west longitude—about equidistant between Iceland and Greenland—where Dönitz assumed British ASW measures to be less intense. At the same time, he ordered four big boats to sail to West African waters to reinforce the three boats already patrolling that area.
Infuriatingly, the OKM insisted that the U-boat force carry out three special missions during April. Two boats were to occupy weather-reporting stations for the benefit of the Luftwaffe at all times. Another two boats were to conduct hunts for British auxiliary cruisers, which had been reported in the Denmark Strait. Yet another two boats (of the southern group) were to escort a German blockade runner, Lech, which was loaded with a “valuable cargo,” from Rio de Janeiro to the Bay of Biscay. “These tasks,” Dönitz complained in his diary, “will probably result in less tonnage sunk and I am bound to call attention to this fact….”
Dönitz had only just established the nine-boat patrol line to the southwest of Iceland on April 1 when U-76, a new VIIB outbound from Germany, discovered the fifty-one-ship convoy Outbound 305 in the Northwest Approaches area, 400 miles to the east! The U-76 was commanded by Friedrich von Hippel, age twenty-six, who had begun the war as a watch officer on Werner Hartmann’s U-37 but had been beached because of chronic stomach problems. The boat had been delayed in training by the Baltic ice and, after sailing from Kiel, had aborted to Bergen with mechanical difficulties. She had been in the Atlantic merely two days.
Because of the “strong” ASW measures in the Northwest Approaches, Dönitz was reluctant to bring the other boats back to the east. He therefore instructed von Hippel not to attack but to track the convoy 400 miles to westward, into the waiting arms of the patrol line, a challenging and risky assignment for a green skipper. The British were almost certain to DF von Hippel’s position reports, go after him, and divert the convoy. Von Hippel hung on, but during that day he ran into “sailing vessels and trawlers” south of Iceland and was forced to run submerged for nine hours to evade detection. When he surfaced to report losing the convoy, Dönitz directed him to “press on” to the west and to do his “utmost” to regain contact.
Meanwhile, one of the new boats in the western patrol line, Eitel-Friedrich Kentrat’s U-74, encountered inbound Slow Convoy 26, twenty-two ships escorted by the 11,400-ton auxiliary cruiser Worcestershire. When Dönitz received this contact report, he instructed Kentrat to shadow and send beacon signals and not to attack until the other boats came up. Herbert Schultze in U-48, who had only one torpedo left and was low on fuel, could not respond, but the other eight boats did, forming the largest pack yet.
The pack commenced attacking late in the evening of April 2. Engelbert Endrass in U-46, who had previously sunk two ships for 10,500 tons, including the 8,700-ton Swedish tanker Castor, on this patrol, led the assault. He sank another tanker, the 7,000-ton British Reliance, and a 4,30Q-ton freighter, but a torpedo that hit the 4,900-ton British freighter Thirlby failed to detonate and another missed the 5,400-ton British freighter Athenic. Eitel-Friedrich Kentrat in U-74 attacked second, sinking a 5,400-ton Belgian freighter and a 4,300-ton Greek freighter and damaging the single escort, the auxiliary cruiser Worcestershire. Helmut Rosenbaum in the new U-73 attacked third, sinking a 5,800-ton freighter and a 6,900-ton tanker, British Viscount, which exploded in flames, brilliantly lighting the seascape.
The British were stunned to learn of U-boats attacking so far west. On orders of the convoy commander, the surviving sixteen ships scattered, some firing guns at real or imagined U-boats. The British, meanwhile, directed other escorts to the scene. A destroyer, Hurricane, escorted the damaged auxiliary cruiser Worcestershire on to Liverpool. Two destroyers, Havelock and Hesperus, searched for survivors of the six sunken ships. Five other warships, including the destroyers Veteran and Wolverine, rounded up the other scattered ships and reformed them into a convoy.
By happenstance, the new boat, von Hippel’s U-76, which was still westbound in search of convoy Outbound 305, ran across the tracks of the scattered ships of Slow Convoy 26. At 0630 on the morning of April 3, von Hippel fired two torpedoes at one of the ships, the 2,000-ton Finnish freighter Daphne. Both missed, but von Hippel tracked submerged and five hours later he sank her.
The other U-boats pursued the reforming convoy eastward. That night, April 3-4, two of the boats caught up and attacked. Herbert Kuppisch in U-94 sank a 5,400-ton British freighter. Robert Gysae, age thirty, in the new VIIC U-98, on his maiden patrol, sank two other freighters. While the destroyer Veteran rescued survivors, the destroyer Wolverine counterattacked the U-boats, driving them off and holding them down, preventing further attacks.
Late in the afternoon of April 4, while running submerged, von Hippel in U-76 sighted another ship from the convoy, the 5,400-ton British freighter Athenic, sailing alone. Von Hippel attacked, firing one torpedo, which hit. The crew of Athenic radioed an alarm and then abandoned ship. Still submerged, von Hippel came in from the other side and fired two more torpedoes. Both hit; Athenic blew up with a thunderous roar.
Upon hearing Athenic’s submarine alarm—SSS—four escorts that were shepherding the remnants of the convoy raced to the scene: the destroyers Havelock and Wolverine (credited with sinking Prien in U-47), the corvette Arbutus (credited with sinking Matz in U-70), and the sloop Scarborough. When they closed the area early on the morning of April 5, von Hippel in U-76 was on the surface, charging batteries. The watch saw one of the escorts and crash-dived. Wolverine obtained sonar contact and notified Arbutus and Scarborough. Bedeviled by a sonar malfunction, Wolverine dropped only two depth charges, one at a time. Arbutus got sonar contact but lost it in the noise of Wolverine’s attack. Coming up, the sloop Scarborough gained a firm sonar contact and fired off eight depth charges.
The ten charges dropped on U-76 fell close. The first single charge from Wolverine smashed all the instruments. The next caused a welded seam to give way, bent a stanchion, and put out all the lights. The eight charges from Scarborough caused severe flooding aft. Believing the boat to be doomed, at 0925, merely four minutes after Scarborough’s attack, von Hippel surfaced to scuttle.
In compliance with the Admiralty’s standing orders, the corvette Arbutus boldly ran in to try to capture a U-boat. While von Hippel and his crew were leaping into the water, Arbutus nuzzled alongside U-76. The first lieutenant of Arbutus, Geoffrey Angus, and three seamen jumped on the forward deck of U-76—the first British in the war to board a German U-boat. While they raced to the bridge to enter the boat and grab the Enigma and secret papers, other hands from Arbutus tied cables and an 8” hawser to U-76 in an attempt to prevent her from sinking. When Angus reached the conning-tower hatch, he saw the boat was “half full” of seawater. The water had mixed with the battery acid, causing strong chlorine gas. Deciding it would be fatal to enter the boat, Angus slammed down and dogged shut the conning-tower hatch to stop the escape of air and to keep the boat afloat.
It was a heroic try, but U-76 was still flooding aft and sinking rapidly. To save herself from capsizing, Arbutus had to let go the wires and hawser, and the boat sank. Wolverine picked up von Hippel and thirty-nine of his crew; Scarborough and Arbutus rescued one man each, for a total of forty-two. The British noted that a seaman on U-76 died when saltwater leaked into the potash cartridge of his escape apparatus, producing a toxic gas that he inhaled.
Counting the survivors of U-70, U-76, U-99, and U-100, the British had captured 113 German submariners (fourteen officers, ninety-nine enlisted men) within one month. Some of these POWs talked freely (or were coerced or tricked into talking freely) and revealed many technical details about the Type VII boats, the organization of the U-boat arm, and the French bases. One of the officers even told the British about the rift that had occurred between Dönitz and Göring over command of the Condors. According to a British intelligence report, another German officer revealed the “astonishing” successes B-dienst had achieved in breaking British naval codes, but that was old stuff.
When Dönitz queried the boats for sinking reports on Slow Convoy 26, he calculated the pack attack had been highly successful: twelve (of twenty-two) ships sunk for 80,000 tons, plus damage to the auxiliary cruiser Worcestershire. He was close. Unknown to Dönitz, the lost U-76 had sunk two ships of the convoy for 7,400 tons, which brought the confirmed total to eleven ships sunk (of twenty-two) for 54,000 tons. The other eleven ships eventually reached port.*
The retreat from the dangerous Northwest Approaches to more distant waters westward appeared to be not a defeat but a stroke of genius in the case of Slow Convoy 26. For the loss of only one (green) boat, U-76, the pack had sunk eleven confirmed ships inbound to the British Isles with full and valuable loads. But the discovery of and success against that convoy was really beginner’s luck. The big expenditure of fuel to get to westward of Iceland severely restricted the ability of the VIIs to hunt and chase the enemy.
A number of those westerly boats had all but exhausted fuel and torpedoes. As a consequence, five boats followed U-48 to France. The high scorer of this returning group was Herbert Schultze in the famous, record-holding U-48, credited with sinking six ships for 40,000 tons on this patrol (confirmed score: five ships for 27,256 tons). Next was Engelbert Endrass in U-46, credited with five ships for 32,000 tons (confirmed score: four ships for 21,778 tons). Two skippers making maiden patrols received high praise: Eitel-Friedrich Kentrat in U-74, who discovered Slow Convoy 26, sank a freighter, and damaged the auxiliary cruiser Worcestershire, and Robert Gysae in U-98, who sank four ships for 15,588 tons. Two skippers making second patrols from France were criticized for failing to make the most of opportunities: Udo Heilmann in U-97, who sank three confirmed ships for 20,500 tons, including two British tankers, the 8,000-ton Chama and 8,100-ton Conus, but had failed to home other U-boats to convoy Outbound 289; and Jost Metzler in U-69, who sank but one confirmed ship for 3,800 tons.
The departure of these boats left only three in the North Atlantic hunting grounds. Three others sailed from France, but two of them were assigned to the OKM-ordered special mission of hunting British auxiliary cruisers in the Denmark Strait. Klaus Scholtz in U-108 carried out this mission successfully, sinking the 16,400-ton Rajputana. Herbert Kuppisch in U-94 had mixed results. On the way into Denmark Strait, he sank the 5,600-ton Norwegian tanker Lincoln Ellsworth, but when he shot at his principal target, an unidentified 15,000-ton auxiliary cruiser, the torpedoes malfunctioned.
The loss of eleven ships (two tankers) in Slow Convoy 26 so far to the west of Iceland speeded up a plan to base substantial British ASW forces in Iceland to extend strong convoy protection farther to the west of that island. This decision, in effect, filled a gap caused by the postponement of the U.S. Navy plan to provide convoy escort on the Iceland-Canada leg and the delays in readiness of the Canadian corvettes.
The Admiralty sent three of the newly formed Escort Groups to Iceland: B-3, B-6, and B-12. These groups were, so to speak, spliced into the center of the North Atlantic convoy run. They were to meet the escorts of westbound convoys at about 20 degrees west and relieve them. Then they were to escort those convoys to about 35 degrees west (900 miles or about five days), whereupon they were to turn about and escort eastbound convoys (Slow, Halifax) back to about 20 degrees west, where they were to hand over convoy protection to those escorts returning to the British Isles. Inasmuch as these escorts had limited range, especially in heavy weather, and had to run into Iceland to refuel, three groups were required to carry out this scheme.
In addition, the Admiralty transferred Coastal Command Sunderlands and Hudsons to Iceland. These planes, equipped with 1.5-meter-wavelength ASV II radar sets, were to provide air protection for the convoys. Although ground facilities were as yet primitive, the aircrews were able to take advantage of the improved April flying weather and the longer days (and shorter nights), which increased opportunities to sight by eye surfaced U-boats.
It should not be imagined that the British suddenly put in place a strong and reliable splice in the North Atlantic convoy run. The new system required terribly rigid convoy routing and escort scheduling. Working on an overly intricate timetable unforgiving of error, the surface and air escort, manned by green crews, often became lost and were unable to find the convoys, throwing everything into confusion. Ships and planes broke down or ran short of fuel and had to abort missions. Inclement weather and the presence of icebergs complicated the linkups. Moreover, the extreme rigidity of the scheme raised the possibility that the Germans might divine the convoy routes and rendezvous and take advantage of the weak links in the splice.
• • •
Dönitz had laid plans for a major U-boat campaign in West African waters during April, employing seven large boats, which were to replenish, as required, from the German supply ships Nordmark and Egerland, parked in mid-Atlantic. But the OKM insisted that two of the boats already in African waters, U-105 (Schewe) and U-106 (Oesten), be detached to escort the blockade-runner Lech from Brazil. Accordingly, the two boats withdrew to waiting stations near the Nordmark, refueling numerous times. While milling around in mid-ocean waiting for Lech to sail, Schewe in U-105 encountered and sank a lone 5,200-ton British freighter, but had no further luck in April. Jürgen Oesten in U-106 sank no ships in April. In response to repeated protests of this waste of firepower from Dönitz, the OKM finally agreed to release one boat, U-105, but insisted that the other, U-106, remain on standby for the Lech voyage.
The diversion of U-105 and U-106 left only one boat off Freetown in, the first half of April: U-124, commanded by Georg-Wilhelm Schulz. After replenishing from Kormoran, Schulz closed the coast and sank three ships for 11,000 tons between April 4 and 8. The last was the 2,700-ton British freighter, Tweed. Coming up to investigate the wreckage, Schulz found that one of Tweed’s two lifeboats had capsized and that several men clinging to it were injured. Schulz fished the survivors from the water and righted the lifeboat. A doctor on U-124, Hubertus Göder, tended the wounded.* Schulz stocked the lifeboat with food, water, cognac, and cigarettes, gave the survivors a course to Freetown, then proceeded with the patrol, sinking three more ships for 15,000 tons off Freetown. He returned to Lorient on May 1, completing a voyage of sixty-seven days. He was credited with sinking twelve ships for about 62,000 tons. Although the confirmed sinkings were reduced to eleven ships for 52,397 tons, it remained one of the outstanding patrols of the war.
Dönitz’s son-in-law, Günter Hessler in the new IXB U-107, led the parade of reinforcements to African waters in April. Following Hessler came Viktor Schütze in U-103 and Heinrich Liebe in the weary IX U-38, then lastly Hans Eckermann in U-A. The U-103 and U-A were forced to abort with mechanical problems. The U-103 resailed in April, but U-A was delayed for weeks.
Southbound, Hessler in U-107 encountered heavy, unescorted traffic. Between April 8 and April 21, he sank five British ships for 30,600 tons, including the 8,500-ton British tanker Duffield. The fifth ship was Calchas, a 10,300-ton freighter. Seeing the crew abandon the sinking ship, or so he believed, Hessler said later, he closed submerged to offer assistance to those in the lifeboats. But “a feeling which I could not explain,” he went on, deterred him from surfacing. As he raised his periscope for a close look, “sailors who had been hiding under the guns and behind the bulwarks, jumped up, manned the guns and opened fire at the periscope.” Hessler pulled down the scope and went deep at full speed, leaving the British gunners an empty sea. This close call cooled Hessler’s humanitarian instincts.
The British were deeply disturbed by these German successes in West African waters. At the peak of Hessler’s onslaught, April 9, the War Cabinet approved a bold and risky plan (Operation Puma) to seize the Spanish Canary Islands. The purpose of the operation was both to deny the Germans use of the islands and to turn them into a British naval base, in part as a facility to counter U-boats in southern waters. The Admiralty formed a strong task force (three aircraft carriers, a battleship, three heavy cruisers, nineteen destroyers), which was to put 10,000 British troops ashore. However, Puma was postponed (and eventually canceled) in favor of tough diplomacy. Churchill demanded that Franco bar German U-boats (and other naval vessels) from the Canaries—or else. Confronted with this pressure, Franco obliged the British.
The denial of the Canaries as a clandestine refueling base did not cause Dönitz to lose sleep. He did not like sending U-boats into the Canaries. British naval forces were closely watching the islands; earlier they had twice denied Clausen in U-37 entry. Franco was not trustworthy. In the uncertain political climate, he might at any time seize and intern any U-boat found in those waters. Dönitz preferred replenishing the boats from German supply ships in the South Atlantic.
In what was developing into a remarkable patrol, Hessler in U-107 sank his sixth British ship, a 7,400-tonner, on April 30. He then withdrew to the mid-Atlantic to replenish from Nordmark and Egerland. Behind him to African waters came Liebe in U-38 and Schütze in the resailed U-103. Schütze sank a 2,300-ton freighter on April 25.