Military history


The twenty Type VIIs that sailed to the Americas in March—the largest deployment of VIIs so far—patrolled the United States East Coast from Maine to Florida. All twenty had made prior combat patrols, twelve of the twenty (60 percent) to the Americas. Only one skipper, Wilhelm Schulze in U-98, replacing Ritterkreuz holder Robert Gysae, was new but his crew was skilled and earlier had made a patrol to Canadian waters. As related, three of the VIIs were commanded by Ritterkreuz holders, two of whom had made prior patrols to Canada: Erich Topp in U-552 and Rolf Mützelburg in U-203. Another Ritterkreuz holder, Adalbert Schnee in U-201, sailed from a long overhaul in Germany. The resupply boats U-A and U-459 were to refuel eight of the twenty VIIs, six of them outbound to America, two of them homebound to France.

Eight of these VIIs sailed in the first two weeks of March for Cape Hatteras. Three refueled in mid-ocean from the U-A: Horst Uphoff in U-84; Hans-Heinz Linder in U-202, who had used much fuel in a failed attempt to find and escort the inbound blockade runner Germania; and Ritterkreuz holder Rolf Mützelburg in U-203, who had also used much fuel in a fruitless chase of a convoy, Outbound North 77, found and reported by Otto Ites, who was homebound from the Americas to France in U-94. The other five boats sailed at one-engine speed, following the Great Circle route.

All eight VIIs inbound to Cape Hatteras found and attacked important targets, which were sailing in Canadian or American offshore waters.

Paul-Karl Loeser in U-373 sank two freighters (one British, one Greek) for 9,900 tons.

Helmut Möhlmann in U-571 sank the 11,000-ton British refrigerator ship Hertford, loaded with meat and dairy products.

Hans-Heinz Linder in U-202 and Horst Uphoff in U-84 each sank 5,200-ton freighters.

Hans Oestermann in U-754 sank the 8,600-ton tanker British Prudence. Ritterkreuz holder Erich Topp in U-552 hit and burned out the 6,300-ton Dutch tanker Ocana, which was later sunk by Allied forces.

Heinz Hirsacker in U-572 (still under a cloud for his balk at the Gibraltar Strait in January) conducted a lackluster small-gun attack on the 6,200-ton British tanker Ensis, which escaped with slight damage.

Rolf Mützelburg in U-203 encountered an unidentified convoy while passing through Canadian waters on March 25, but his attack was thwarted by “well-aimed” depth charges from escorts.

Seven of these eight boats reached the Cape Hatteras area in late March and early April, overlapping Hardegen in U-123. Notwithstanding the intensified American ASW measures and a bright, full moon, three of the boats found good hunting. In a spectacular week’s work, April 3 to April 10, Erich Topp in U-552 sank six more ships (four tankers)* for about 40,000 tons, the best performance by any Type VII skipper in American waters. In the period from March 31 to April 6, Hans Oestermann in U-754 also sank six more ships for 23,000 tons: a freighter, two tankers (American Tiger, 6,000 tons; Norwegian Kollskegg, 9,900 tons), and a tug and two of her three barges. Although his hydrophones were out of commission, “making shallow water operations difficult,” Helmut Möhlmann in U-571 sank the 10,000-ton Norwegian tanker Koll and two freighters. Mützelburg in U-203 claimed sinking three tankers and a freighter for 36,000 tons, but two of the tankers escaped, only damaged, reducing his confirmed score to one freighter and the 8,100-ton British tanker San Delfino. Hirsacker in U-572 sank two freighters for 9,500 tons and damaged a tanker. Arriving last, Uphoff in U-84 sank one 3,000-ton freighter. Neither Linder in U-202 nor Loeser in U-373 sank a ship off Cape Hatteras.

The total bag for these first eight boats was a slaughter: twenty-six ships (ten tankers) for nearly 150,000 tons, counting Topp’s tanker, Ocana.

It had been expected that the refueling from supply boats was to increase substantially the patrol days of the VIIs in American waters. In reality, that was not the case. The three boats that refueled from U-A outbound to America were at sea an average of fifty-five days. Two others homebound to France, Möhlmann’s U-571 and Hirsacker’s U-572, refueled from the tanker U-459, extending their patrols to an average sixty days. Hence, the average time at sea for the five boats of the group that refueled, inbound or outbound, was fifty-seven days. The average time at sea for the three boats that did not refuel was fifty days, making the average gain for the boats of this group that refueled merely seven days.

Nor did refueling increase the ship sinkings by this group. The five of eight boats that refueled, inbound or outbound, sank ten ships—an average of two victims per boat. The three boats that did not refuel sank sixteen ships—an average of 5.3 victims per boat. Sinkings still depended upon the skill and aggressiveness of the skippers and crews, weather, opportunity, luck, and availability of torpedoes. Some skippers of this group (Topp and Mützelburg, for example) ran out of torpedoes. Replenishment and resupply could not be fully exploited until a means of providing the boats with torpedo reloads could be arranged.*

Erich Topp’s claims for this and prior patrols exceeded 200,000 tons, and he therefore qualified for Oak Leaves to his Ritterkreuz. Hitler announced the award by radio on April 11, while Topp was homebound. Later, the Führer presented the medal to Topp at Wolfsschanze, at the same time he awarded Hardegen his Oak Leaves. Although Topp had his choice of virtually any assignment, he preferred to remain in combat with U-552. He thus became the leading “ace” at the front.

The other twelve VIIs sailed, day by day, during the second half of March. This group included Ritterkreuz holder Adalbert Schnee in U-201, on his first patrol to the Americas, and several promising skippers, among them Peter Cremer in U-333, exonerated for the accidental sinking of the blockade runner Spreewald; Siegfried von Forstner in U-402; and Heinrich Zimmermann in U-136. Cremer had made a prior patrol to Canada. Like Schnee, von Forstner and Zimmermann were on their first patrols to American waters.

Outbound, three of the VIIs of this group of twelve refueled from U-459: the veteran U-98, commanded by the new skipper, Wilhelm Schulze, age thirty-two; Peter Cremer in U-333; and Werner Schulte in U-582, who had used much fuel attempting without success to meet and escort the blockade runner Rio Grande into France.

While Schulte in U-582 was en route to his refueling rendezvous with U-459 on April 16, the American submarine R-1, on ASW patrol, shot four torpedoes at her. Credited with a U-boat kill, the first by an American submarine, the R-1’s skipper, James D. Grant, was awarded the Navy Cross. But U-582 had escaped the encounter undamaged and replenished as planned.

Refuellings were difficult. None of the VIIs had ever practiced the procedure. The crews had not even been properly briefed, the technical adviser on U-459 wrote. To carry out a refueling, which took one and a half to five hours, the sea had to be relatively calm and the seamanship excellent. The U-tanker went ahead at 3 to 4 knots on electric motors and floated a towing hawser and oil hose back to the boat to be refueled. Usually everything went wrong, the adviser went on:

In the case of 8 [of 15] boats, mishaps occurred causing greater or lesser delays, through hose leakages caused by poor maneuvering, by repeated passing-over of hoses, by inept handling on deck (chafing and tearing because of the lack of chafing mats …) or through hooks on the diving planes. While the hoses were being passed over, one boat fouled the hoses with its forward hydroplanes, tore the hawser and both hoses away and, when this was cleared, let go the whole equipment…. [However] the crew [of U-459] behaved magnificently in these operations, which were often most difficult, pushing themselves to the limit of physical endeavor. For example, the provisioning of 4 boats in a period exceeding 16 hours in one day; on another day working 8 to 10 hours with lifelines attached, with seas and breakers constantly washing over them.

The U-459 doled out its fuel and food sparingly on a rigid schedule drawn up by U-boat headquarters. Most VIIs received about 30 cubic meters of fuel (about 30 tons) and a week to ten days’ supply of food, including fresh bread baked in a special facility on board U-459, which could produce eight loaves per hour.

Schulte in U-582 had spent three weeks on the abortive rendezvous with Rio Grande, and was very low on fuel when he reached U-459. He was allotted 55 cubic meters (about double the usual quota), but even this was not enough to safely carry out an aggressive patrol in United States waters. Dönitz therefore diverted him to the island of Bermuda, about 600 miles southeast of New York. There Schulte encountered heavy weather, scant shipping, and “strong” ASW measures. Hounded by aircraft and patrol boats, he shot a triple bow salvo at a “fast passenger ship” but missed. He returned to France with no sinkings to credit—an exceedingly frustrating voyage—and, of course, a refueling to little purpose.

The other eleven VIIs of this group closed on the United States coast from New York to Florida. Several went to the Cape Hatteras area to replace the VIIs that had sailed earlier in the month, arriving just ahead of or during the onset of the new moon, April 14. Among these new arrivals was Eberhard Greger in U-85, embarked on his fourth war patrol. Southbound off New Jersey on the night of April 10, he sank the 4,900-ton Swedish freighter Christina Knudsen with two torpedoes. In the evening of April 13, concealed by the darkness of the new moon, Greger lay in wait in shallow water off Bodie Island, north of Cape Hatteras.

That same day, the four-stack Roper sailed from Norfolk to Cape Hatteras on ASW patrol. Commanded by Hamilton W. Howe, Roper was armed with five 3/50 caliber guns, six torpedo tubes, and seventy-five 300-pound depth charges, which could be rolled from her stern tracks or shot from Y and K guns. She had recently been equipped with a British-built Type 286 meter-wavelength radar.

Just after midnight, April 14, while southbound off Bodie Island, Roper got a radar contact at 2,700 yards. Inasmuch as these waters were teeming with smaller Navy and Coast Guard patrol boats, fishing trawlers, tugboats, and salvage craft, initially the contact caused no great excitement. Roper routinely turned to run down the bearing. While doing so, sonar picked up the noise of fast screws. That report caused excitement. The contact was moving too fast to be the usual patrol or fishing boat.

The radar contact was U-85. Trapped by a destroyer in water only 100 feet deep, Greger had two choices: to dive and possibly be pounded to pieces by depth charges, or to run at full speed on the surface to deep water. Perhaps hoping he could shake the destroyer in the darkness, Greger chose to run. But he did not know the destroyer had radar. Despite numerous indications to the contrary, Dönitz and his submariners still believed that radar was too big, bulky, and sensitive for installation on small ships.

Chasing at 20 knots, Roper gradually overhauled U-85. In a last but futile effort to rid himself of the pursuer, Greger fired his stern tube at 700 yards. The torpedo missed, running close down Roper’s port side. When Roper closed to 300 yards, and appeared to be coming in to ram, Greger gave the order to scuttle and abandon ship. To facilitate this final, desperate act and get out of Roper’s way, Greger abruptly turned hard to starboard.

When U-85 turned, Roper switched on her 24” searchlight and opened fire at point-blank range. Seeing the Germans running on deck to abandon ship, the excited Americans, they said later, concluded they had come up to man U-85’s deck gun to shoot it out.* In reaction, the Americans raked the U-boat’s deck with machine-gun fire, cutting down the Germans who were trying to jump over the side.

With her sea cocks open, U-85 quickly flooded and went down by the stern in ninety-eight feet of water. As she did so, the Americans, as they said later, saw “about forty” Germans in the water or on the deck of U-85, many crying out in German, “please save us.” Roper thus had the opportunity to capture U-boat prisoners for intelligence and propaganda purposes, and there was a good possibility that in such shallow water Navy divers could enter U-85 and recover a four-rotor Enigma, the new short-signal book, and other secret materials. But the excited Americans apparently did not give these matters any consideration. Roper swung around, charged through the German survivors in the water, and dropped eleven depth charges set for fifty feet, directly on top of U-85. Those Germans who were not cut to pieces by Roper’s propellers were killed by the depth charges. Not one man of the crew survived. The force of the explosions shattered U-85 externally and internally and rolled her nearly flat in the sand on her starboard side.

Fearing other U-boats might be near—the fate of sister ship Jacob Jones perhaps fresh in mind—Roper radioed an account of her attack and hauled away. After daylight, a Catalina, a blimp, and five other aircraft appeared. The Catalina spotted the German bodies and bits of wreckage and dropped a depth charge for good measure. Other aircraft drew Roper back to the scene with smoke flares. Roper, too, dropped another depth charge, then lowered away two boats to collect the bodies and debris. In the midst of this gruesome operation, Roper’s sonar reported a U-boat contact—perhaps the hulk of U-85—and she broke off to fire four more depth charges to no purpose.

Roper’s boats found thirty-one German bodies. Two of them were badly mangled. After searching the clothing of these two, Roper’s men callously left them in the sea. The other twenty-nine bodies were brought on board, stacked on deck, and covered with a tarpaulin. Roper dropped two more depth charges on U-85, then headed triumphantly for Norfolk. Outside the harbor, a Navy tug, Scioto, took off the twenty-nine bodies. After they had been searched again (two useful diaries were found), photographed, and fingerprinted, they were buried in marked graves with full military honors in the National Cemetery, Hampton, Virginia, in coffins provided by the Veteran’s Administration.

The Navy immediately initiated efforts to salvage U-85 and/or to recover her intelligence materials. Numerous small craft, including two of the twenty-two* newly arrived British ASW trawlers, Bedfordshire and Saint Loman, swarmed over U-85. Early in these operations, hard-hat divers found an armed but unexploded depth charge lying on the bottom alongside U-85. A Navy demolition team exploded the charge, no doubt further damaging the boat. Between April 15 and May 4, Navy divers made about one hundred descents to the wreck. Inasmuch as she was lying nearly flat on her starboard side, none of the divers could get inside the boat to look for her Enigma or other intelligence material. Because of the depthcharge damage to her air lines and tankage, she could not be raised—or even righted—by salvage air.

When it was finally decided that U-85 could be raised only by “extensive” use of pontoons, the salvage effort was abandoned. The divers stripped U-85 of much topside gear—the 20mm bridge gun, the IZO torpedo aimer, and the gyro-compass repeater—and “dismantled” the 88mm deck gun, which still had the tampion in the muzzle. But they could not pry open the storage canister and remove the topside torpedo. They reported no evidence of gun hits by Roper and concluded that U-85 was “probably scuttled.”

Several other VIIs were near Cape Hatteras when Roper sank U-85. The Bucket Brigade convoy scheme between Key West and New York was in operation by that time, and aircraft patrolled Hatteras from dawn to dusk. There was no authorized ship traffic at night. Daytime U-boat operations close to shore where the Bucket Brigade convoys sailed were hazardous.

Two of the VIIs mounted attacks. Near sunset on April 17, Ritterkreuz holder Adalbert Schnee in U-201 found and damaged a 7,500-ton tanker, but—awkwardly—it turned out to be the Argentine neutral Victoria. American naval vessels rescued the crew and eventually confiscated the ship from the pro-German Argentines, setting in train a diplomatic uproar that ultimately drew an apology to the Argentines from Berlin. In the late afternoon of April 18, Heinrich Zimmermann in U-136 boldly attacked an eight-ship Bucket Brigade convoy, which was escorted by the hard-working 165-foot Coast Guard cutter Dione, two British ASW trawlers, a small patrol boat, and several aircraft. Zimmermann fired two torpedoes at the loaded 9,000-ton American tanker Axtell J. Byles.One torpedo broached, alerting the escort; the other hit, blowing a hole in the tanker, but she survived and reached Norfolk. Dione responded with a salvo of eight depth charges and called in eight aircraft, which dropped more depth charges and bombs. However, Zimmermann escaped undamaged.

It was not yet apparent to Dönitz, but the fact was that, however thin and green, by mid-April American ASW air and surface forces, augmented by the British ASW trawlers, had rendered the Cape Hatteras area and most of the continental shelf unproductive for U-boat operations. Several VIIs of the March group dutifully remained near Cape Hatteras, but after April 20, as Dönitz noted later, none had any success and most reported “strong” ASW patrols.

Granted freedom of action, most of the VIIs hauled away from Hatteras. These and others patrolled several hundred miles offshore, beyond range of most air patrols, loosely covering the sea lanes from Massachusetts to Georgia. An exception was Siegfried von Forstner in U-402, who had sunk one freighter inbound but none in a frustrating week off Hatteras. At the end of his patrol, he hugged the shallow North Carolina coast south to Cape Lookout and Cape Fear. There he sank the 5,300-ton Russian tanker Ashkabad and a big (215-foot, 1,000-ton) but ancient (1906) yacht, Cythera, which the Navy, for the second time in two world wars, had acquired and converted to an escort/rescue vessel.

The Russian Ashkabad sank in shallow water and her skipper believed she could be salvaged. But according to the writer Gary Gentile, the destroyer Semmes, uninformed of this prospect, came along and destroyed her with gunfire to clear the ship channel. Hit by two torpedoes, the ancient yacht Cythera blew to pieces. As she sank, her armed depth charges exploded, killing all but two enlisted men of the seventy-one-man crew. Von Forstner fished both from the water and took them back to Germany—the first American naval POWs to be captured by the Germans. Both were to survive the war.

The hunting offshore was spotty:

• Ludwig Forster in U-654, who had sunk a 7,000-ton British freighter inbound, sank two other freighters 300 miles east of Hatteras for a total of 17,755 tons, making him the high scorer of this group.

• Second place went to Ritterkreuz holder Adalbert Schnee in U-201, who sank three freighters for 15,300 tons by torpedo and gun, 400 miles east of Georgia. Schnee also had a fleeting glimpse of the liner Aquitania, inbound from Australia to New York to take American troops to Northern Ireland, but she was going very fast and there was no way he could overtake her.

• Karl-Ernst Schroeter in U-752 got wartime and postwar credit for sinking three ships for 15,500 tons by torpedo and gun, but research by Gary Gentile has disallowed one, the 4,800-ton Norwegian freighter Reinholt, which was only damaged by gunfire.

• After his abortive attack on the Bucket Brigade convoy, Zimmermann in U-136 went north to New Jersey and New York waters, where he sank two freighters for 12,400 tons, the second, the Dutch Arundo, merely fifteen miles east of the Ambrose lightship marking the channel into New York harbor. On his way home he attacked the 300-ton Canadian sailing ship Mildred Pauline by gun. He reported that he had “missed,” but in fact, she went down.

• Günther Heydemann in U-575 turned in a second disappointing patrol to the Americas, sinking only one ship for 6,900 tons while inbound.

Worse yet, two VIIs sank no ships at all: Walter Schug in U-86 and Wilhelm Schulze, the new skipper of the veteran U-98, who had refueled from U-459 inbound to America. Both skippers shot at freighters, but missed. Caught by a “destroyer” in fifty-nine feet of water off Florida, Schulze in U-98 fired four torpedoes at his assailant, but missed. In retaliation, the (as yet unidentified) “destroyer” carried out a “heavy” depth-charge attack, Schulze reported, but it was not “persistent” and thus he was able to escape.

Having suffered a two-day engine breakdown and refueled from U-459, Peter Cremer in U-333 also headed for Florida waters. On the afternoon of April 30, while 300 miles east of Jacksonville, he spotted the masts of the modern 11,000-ton, double-hull tanker British Prestige, zigzagging at 10 knots, loaded with highoctane aviation gasoline. Cremer tracked her until dark, then fired two bow torpedoes. When both missed, he submerged, reloaded the tubes, then surfaced to pursue, hampered by a very bright moon. Hauling around, he submerged for a periscope attack, closing to point-blank range, silhouetting the big ship against the moon. As he was on the point of firing, the zigzagging British Prestige unwittingly rammed U-333. The tanker lurched to starboard, the startled skipper reported, and the crew heard a loud “rumbling crushing noise.” It was obvious the ship had hit a submerged object—U-boat? whale?—but she did not pause to investigate. Unknown to the captain or crew, her outer hull was ripped open from stem to stern.

The collision severely damaged U-333. Her stem was “twisted to port,” jamming shut the two port bow torpedo tubes. The bridge structure was mangled; the attack periscope was bent to port at a crazy angle and could not be retracted. Had Cremer aborted the patrol, no one would have reproached him, but it was his second mistake in as many patrols—sinking Spreewald had been the first—and there was the possibility that he might lose his command. He therefore set his crew to work with welding torches and mallets to cut and hammer U-333 back into operable condition. Remarkably, the men succeeded, and Cremer closed the Florida coast near Fort Pierce with his “half-wrecked” boat.

Cremer lay silently on the surface in bright moonlight on May 5, fifteen miles offshore in twenty-six feet of water. At about midnight, the 8,300-ton American tanker Java Arrow, a straggler from a Bucket Brigade convoy, came along southbound, in ballast. Cremer fired two torpedoes by eye. Both hit and the ship “burned furiously” and sank, or so Cremer believed. Actually, she was salvaged and returned to service. Four hours later, when the 1,300-ton Dutch freighter Amazone appeared, Cremer fired two more torpedoes. Both hit and Amazone went down. Two hours later—near dawn on May 6—yet another ship loomed up, the 7,100-ton American tanker Halsey, northbound with a load of naphtha and fuel oil. Cremer fired two bow and one stern torpedo at her by eye. The two bow shots hit and Halsey exploded in a fireball and sank.

American ASW forces responded vigorously to this last sinking. First on the scene was PC-451, a prewar Navy prototype, manned by the Coast Guard. The force of her depth charges slammed U-333 into the sand at sixty-six feet, froze her hydroplanes, and caused other external and internal damage. Then came sister ship PC-450 and the 125-foot Coast Guard cutter Vigilant, and two other smaller Coast Guard patrol boats. But Cremer managed to outwit these attackers, clawing along the sandy bottom toward deep water—197 feet—his thrashing propeller noises drowned out by the errant depth-charge explosions.

After fifteen hours of brutal punishment and nerve-stretching tension, Cremer got away, or so he thought. An aircraft had followed U-333’s leaking oil trail and had brought up the four-stack Dallas, en route from the Navy’s sonar school in Key West to Charleston. But Dallas was not equal to the challenge. After dropping twenty-five 300-pound depth charges, she resumed her voyage, and by what the Germans deemed “a miracle,” U-333 escaped, battered but undaunted.

Cremer was not finished. Limping home in the dark and rainy early morning hours of May 10, 500 miles east of Florida, he ran across the 5,200-ton British freighter Clan Skene sailing alone. He fired his last two bow torpedoes. Both hit and the ship went down. Upon hearing the full and amazing story of Cremer’s patrol, Dönitz awarded him a Ritterkreuz. Cremer’s first patrol to America had ended with a court-martial, his second in a blaze of glory and publicity.*

Hans-Dieter Heinicke in U-576, making his second patrol to American waters, hit and sank a 5,100-ton bauxite freighter 400 miles east of Hatteras, then headed toward Cape Cod, Massachusetts. Passing northbound off New York, he shot at the Norwegian freighter Tropic Star. One torpedo hit but failed to explode, and the lucky Tropic Star sailed on. Off Cape Cod in the early hours of April 30, Heinicke found a formation of freighters, possibly a Boston-Halifax convoy. He fired his last torpedoes at four overlapping ships, hitting the 1,300-ton Norwegian Taborfjell, loaded with Cuban sugar. She sank. Three of her crew survived and were rescued by the British submarine P-552, one of the nine American submarines recently loaned to the Royal Navy.*

Later that day, April 30, Heinicke spotted the most impressive group of targets yet found in American waters. It was the American troop convoy AT 15, composed of seven transports, including Aquitania, bound from New York to Argentia, Iceland, and Northern Ireland. Traveling at 12 knots, it was escorted by the battleship New York, the light cruiser Brooklyn, the new British “jeep” carrier Avenger (in transit), and fourteen destroyers, as well as air patrols. It was to join another troop convoy, NA 8, composed of four troopships sailing from Halifax on May 3, which increased the total number of troopships to eleven, with 19,000 troops embarked.

Having no torpedoes, Heinicke could only grind his teeth in frustration. After the formation had passed within firing range, he surfaced to shadow and report, but one of his diesels broke down. Consulting his plotting board, Dönitz saw that there were four VIIs inbound to America within 600 to 1,000 miles of the convoy. Although he did not believe there was much hope of an interception, he felt obliged to try, in view of the valuable targets entailed. He directed the four boats to proceed at full speed and to form a patrol line, running due south from Cape Race, Newfoundland, and urged Heinicke in U-576 to make every possible effort to regain contact.

After getting his diesel back on line, Heinicke did, in fact, regain contact, at about the time convoys AT 15 and NA 8 merged, on May 3. However, he reported “strong” air escort forced him off and down and thereafter he “lost” the convoy again. Acting on Heinicke’s latest report, Dönitz shifted the four-boat patrol line thirty miles north—closer to Cape Race—directly into the shallow fog-shrouded waters of the Grand Banks. However, none of the five boats found the convoy, and Dönitz canceled the operation.

In all, the twenty VIIs that sailed to the Americas in March sank forty-six confirmed ships (twelve tankers) for about 242,000 tons, nearly a third of the total (thirteen ships for 71,000 tons) accounted for by two skippers, Erich Topp in U-552 (five tankers) and Hans Oestermann in U-754 (three tankers). It was a spectacular foray—the high point for the VIIs in American waters—but a close analysis by the U-boat staff revealed a disappointing trend. The average sinkings per patrol of the March group declined sharply from those of the VIIs of the February group: down from 3.2 ships for 18,651 tons to 2.3 ships for 12,097 tons. Moreover, contrary to many accounts—and the myths arising later—the first big refueling operation of VIIs had not resulted in increased sinkings. The eight VIIs of the March group that replenished sank an average of only 1.6 ships for 9,396 tons per patrol. Three refueled VIIs sank no ships: Schug in U-86, Schulze in U-98, and Schulte in U-582.

Owing to the increase in average sinkings by the Type IXs, in aggregate the twenty-six boats of the March group almost exactly duplicated the aggregate sinkings of the twenty-six boats of the January group: seventy-five confirmed ships (twenty-five tankers) sunk for 406,046 tons. This was another severe blow to Allied shipping. However, when it is taken into account in this comparison that one January boat aborted, that eight others were manned by green skippers and crews, that all the January VIIs patrolled in the more heavily defended Canadian waters, that the weather was far less favorable, and that eight of the March boats refueled, it was less of a blow than might have been expected.

The failure of the more experienced boats of the March group to significantly exceed the aggregate returns of a like number of January boats was a certain indication that the provisional convoying measures and ASW in the Eastern Sea Frontier were beginning to take effect. The loss of Greger’s U-85, the near losses of Hardegen’s U-123 and of Cremer’s U-333, and the vigorous counterattack incurred by Zimmermann in U-136 during his assault on a Bucket Brigade convoy, were other indications. Since a steady improvement in ASW measures in the Eastern Sea Frontier was expected, Dönitz and his staff drew plans to shift the weight of the U-boat campaign to the less well-guarded shipping lanes in the Gulf of Mexico and the Caribbean.

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