Hitler’s U-Boat War- The Hunted 1942-45

by Clay Blair

  The British had failed to produce a reliable four-rotor bombe, Engstrom wrote. “In the original discussions of this [4-wheel bombe project] with the British, the U.S. Navy was [only] to assist GC&CS in the German Naval problem.… British production of 4-wheel bombes has been extremely unsatisfactory. According to the latest information, eighteen (18) have been produced and continued operation of three (3) is the average performance.… At present the principal burden of the naval problem is carried by the U.S. Navy bombes.” To buttress his estimates and assertions, Engstrom quoted from a message from GC&CS to OP20G on March 24, 1944:

  Performance of our machines is still poor and likely to remain so. In view of your 4-wheel capacity being more than adequate, priority is being given here [in England] to the production of new 3-wheel machines.‡

  In February 1944, Hugh Alexander/who had succeeded Alan Turing in Hut 8, Bletchley Park, visited Washington and urged the U.S. Navy to build fifty more four-rotor bombes. “This was the first intimation that the U.S. Navy would be asked to extend its endeavor in this direction,” Engstrom wrote. “Although a pessimistic outlook on the Atlantic situation can justify the additional equipment for Naval work, it is undoubtedly true that the prime impetus for the expansion lies in [American help in solving] the [German] Army and Air Force keys.”

  The case Alexander presented to Washington was persuasive. On February 25, Admiral King directed the contracting agent, the chief of the Bureau of Ships, to purchase the requested fifty improved production bombes, designated Model N-1530. “The operation of these additional bombes under [U.S.] Navy jurisdiction will, of course, speed up by one-third the recovery of Naval keys “ Engstrom judged. “It will also increase by one-third the time devoted to non-Naval problems,” such as German Army, Luftwaffe, and other networks.

  The “pessimistic outlook” on the “Atlantic situation” to which Engstrom referred arose from the aforementioned discovery in March that the Germans intended to make a “major change” in Enigma to increase its complexity. As was soon learned, this was to be the inclusion of an internal reflector (“D”) that could be rewired by the operator. The Germans had introduced this reflector on “certain air circuits” (i.e., Luftwaffe networks), causing “some concern,” Engstrom wrote in vast understatement.

  To deal with a possible inclusion of a “pluggable reflector” on naval Enigma machines, Engstrom stressed, a new type of decoding machine would be required. Engstrom and his R&D associates had anticipated the possibility of a “pluggable reflector” a year earlier (April 1943), he asserted, and the National Cash Register Company had almost completed a machine to cope with it. Called “Duenna,” or N-1500, it was similar to a bombe but a completely “separate device.” The Duenna under construction was twenty feet long, nine feet high, and four feet wide. It weighed eight thousand pounds (four tons). At Engstrom’s insistence, the Duenna was awarded a higher priority than the fifty new model N-1530 production bombes, although there was no slack in either project.

  Wenger and Engstrom explained their position in another document in April 1944:

  In our opinion there is serious question as to the necessity for building all of the [fifty] additional bombes. Certain important changes [pluggable reflectors] are apparently underway in the German Enigma machine which, if carried through as expected, will require use of a different type of machine [i.e., Duenna] designed by the Research Group of OP20G. The extent to which the [standard] bombe will be useful if these expected changes become extensive, is questionable.

  We are taking all reasonable steps to provide for eventualities. In order to insure meeting the problem when it arises, we are proceeding with the design and construction of ten (10) of these new units [Duennas] and may find it desirable to build, at most, only a portion of the additional [fifty standard] bombes [as requested by the British]. While the position as far as the Germans are concerned is not clear at the present time, we expect some clarification prior to the completion of the [standard] bombes, and, should it appear advisable, we shall recommend a reduction in the number to be built.

  The overwhelming success of Overlord, the invasion of Occupied France that took place about ten weeks after Wenger and Engstrom wrote those words, evidently swept away the “pessimistic outlook” about codebreaking in the Atlantic sector. For one thing, the Germans soon lost the telephonic lines between U-boat Control in Berlin and the five U-boat bases on the Atlantic coast in France and were forced to use radio. For another, significantly more U-boats put to sea, generating naval traffic. These developments led to a sudden enormous increase in the flow of naval Enigma on various radio circuits and with it, an inevitable increase in procedural errors that produced a bountiful harvest of the cribs necessary to feed to the bombes. For another thing, the Allied invasion apparently caused the Germans to cancel plans for widespread distribution and introduction of the “pluggable reflector.”

  The upshot was that in September 1944, after the National Cash Register Company had completed half (twenty-five) of the new model N-1530 bombes requested by the British, Admiral King directed the Bureau of Ships to cancel the remainder. That left the number of American bombes built in the war at 121 (ninety-six plus twenty-five). The machines cost a total of about six million dollars, Engstrom estimated. By March 1945, shortly before the German surrender, only two giant Duennas (N- 1500s) had been completed and put into operation and only three more were on order.

  The U.S. Army’s project to build Rapid Analytic Machines (RAMs), or three-rotor bombes, encountered as many setbacks as the British four-rotor bombe project. Bell Telephone Laboratories built only ten. By comparison to the U.S. Navy bombes, they were painfully slow: 910 “tries” of crib assumptions per second compared to the Navy’s 20,280. In a typical day, a Navy bombe could therefore make 40,000 short three-wheel runs compared to the Army’s 1,200. “The total U.S. Army installation can be considered equal to about one of our bombes,” Joe Wenger wrote on .February 16, 1945, comparing the two types. “To duplicate Navy production figures with bombes of the Army type would require a tremendous installation. ... A rough estimate of the relative productive capacity of the complete U.S. Army and U.S. Navy installations is a factor of fifty in favor of the Navy.”

  PATROLS TO WEST AFRICA

  Ten Type IXs patrolled to Freetown and the Gulf of Guinea in the period from January 1 to June 1, 1944. They were to be supported by the Type XIV “Milk Cow” U-tanker U-488. Five of this group and the U-tanker failed to return.

  The famous IXB U-123, in which Reinhard Hardegen opened the Drumbeat campaign in United States waters, sailed on January 9, commanded by Horst von Schroeter, age twenty-four. The senior petty officer was Walter Kaeding, age twenty-eight, who had commissioned the boat in May 1940 and had made all thirteen of her war patrols under Moehle, Hardegen, and von Schroeter.

  Von Schroeter found no targets off Freetown. On the return voyage, he met and refueled from the XIV tanker U-488 on March 23. Reporting this meet, U-488 said that the radio in U-123 was out and unfixable and relayed von Schroeter’s results: a triple miss on a troopship, a T-5 miss on a “destroyer,” no hits or sinkings. Control then directed von Schroeter to rendezvous with the outbound U-505 on April 7 and get new Enigma keys. When the boat arrived in Lorient on April 24, completing a fruitless voyage of 107 days, Control retired U-123. Admiral Dönitz awarded von Schroeter, Kaeding, and the chief engineer Reinhardt König the Ritterkreuz.* Von Schroeter and König returned to Germany to commission a big “electro boat.” Promoted to officer rank, Kaeding briefly commanded a school duck, then a small “electro boat” that was never completed.

  Next to sail was the no less famous IXC U-66, commanded by a new skipper, Gerhard Seehausen, age twenty-six. Passing Cape Finisterre, Seehausen saw a carrier and screen and boldly attempted an attack but he only managed to shoot one T-5 at a “destroyer,” which missed. Off Freetown he missed another “destroyer” with a T-5. Proceeding east in the Gulf of Guinea, on February 26 he came upon a small convoy of
f Takoradi, STL 12, and sank the 5,300-ton British freighter Silvermaple and took her captain and another officer prisoner. He claimed another freighter from this convoy but it wasn’t confirmed. In the week following, Seehausen sank two lone freighters: the 5,200-ton French St. Louis and the 5,000-ton British John Holt. Still later in March, he got the 4,300-ton British tanker Matadian in the shallow Bay of Nigeria. In return, British patrol craft savaged U-66 with depth charges and forced her to bottom in tenacious mud at four hundred feet. Seehausen finally escaped by sallying ship fore and aft.

  Having sunk what he believed to be an impressive five ships for 30,688 tons (actually, four ships for about 20,000 tons), Seehausen commenced the homeward voyage, low on fuel. Aware of his need for fuel, U-boat Control ordered Seehausen to rendezvous with the U-tanker U-488 on April 26. Allied codebreakers decrypted Enigma messages about this rendezvous and American naval authorities put a hunter-killer group on the scent: the “jeep” carrier Croatan and five destroyer escorts. Upon reaching the rendezvous area, the Americans DFed signals between U-66 and U-488 and Croatan launched Avengers configured for prolonged night-search flights.

  The night searchers found U-488, and in the early hours of April 26, all five destroyer escorts converged for an attack with depth charges and Hedgehogs: Barber, Frost, Huse, Inch, and Snowden. The attack was deadly. The U-tanker was never heard from again. Tenth Fleet credited four of the five ships (not Inch) with this important kill that left only one XIV tanker, the U-490, which, as described, was sent to the Far East and lost.

  Nearby, Seehausen in U-66 heard the attack on U-488. He hauled off and radioed Control: “Supplying impossible.... Noise of sinking heard....” Upon receiving this message, U-boat Control repeatedly queried U-488. When she did not reply, Control correctly assumed the worst and attempted to rendezvous U-66 with Lüdden’s U-188, inbound from Penang, and the outbound U-68. Meanwhile, Control declared further refueling at sea to be “impossible” (until the development of submerged refueling) and warned the boats in distant areas to plan return voyages accordingly.

  Seehausen in U-66 proceeded to the rendezvous with U-188 as related, but the Americans pursued him relentlessly. Two hunter-killer groups—the “jeep” carriers Block Island and Bogue with appropriate screens—relieved the Croatan group, which was low on fuel. Reporting the failure of the rendezvous, Seehausen added: “Supplying impossible since [we have been] DFed constantly since [April] 26th. ... Mid-Atlantic worse than Biscay.” On the night of May 5-6, a night-flying Avenger from Block Island, piloted by Jimmie J. Sellars, found U-66 and homed in one of the destroyer escorts, Buckley, commanded by Brent M. Abel, a graduate of Harvard College and Harvard Law School, who that day celebrated his twenty-eighth birthday.*

  Sighting U-66 silhoutted against the moon, at four thousand yards, Buckley prepared to attack and ram. However, Seehausen saw Buckley first, possibly shot a T-5, and opened fire with his machine guns and flak guns. Abel returned fire from 2,100 yards with his three 3” guns, which knocked out U-66’s 4.1” deck gun, caused other damage, and probably killed or wounded some Germans. Buckley then rammed U-66 forward and the two ships locked in a deadly embrace, reminiscent of the battle between U-405 and the American destroyer Borie.

  Seehausen feared that Buckley’s men were about to board U-66 in an attempt to seize secret materials. Since that action would force him to scuttle with most of the crew belowdecks, he directed his first watch officer, Klaus Herbig, age twenty-two, and other men on the bridge to board Buckley and create a diversion while he broke away from Buckley, got the rest of the U-66 crew topside, and scuttled. “Immediately,” Herbig recalled, “I jumped over with eight men to where we could hang on to the rail of the destroyer.”

  When these Germans appeared on Buckley’s bow—to divert and/or to surrender—the Americans, believing they intended to capture Buckley, repelled them hand-to-hand as in days of yore. Abel described the counteraction in his official report:

  Men begin swarming out of submarine and up on Buckley’s forecastle. Machine gun, tommy gun and rifle fire knock off several. Ammunition expended at this time included several general mess coffee cups, which were on hand at ready gun station. Two of the enemy were hit in the head with those. Empty shell cases were also used by crew of 3” gun Number 2 to repel boarders Buckley suffers only casualty of engagement when man bruises fist knocking one enemy over the side.... The boatswain’s mate in charge of forward ammunition party kills a man attempting to board with .45 pistol. Man falls back over side. Midships repair party equipped with rifles mans lifelines on starboard side ... and picks off several men on deck of submarine. Chief Fire Controlman uses tommy gun from bridge with excellent results.

  The Buckley crew killed or fatally wounded an unknown number of Germans and captured five, including Herbig. Meanwhile, Seehausen broke U-66 loose from Buckley and sped off in the darkness at maximum speed, leaving a string of Germans who were jumping into the sea. Notwithstanding a distended bow and other collision damage forward, Abel in Buckley chased with guns blazing, caught up, and prepared to ram U-66 a second time. In the chaos of this close encounter, U-66 swung around and rammed Buckley aft, wiping off her starboard propeller shaft and holing her plates. Thereupon the U-66 chief engineer, Georg Olschewski, who had been awarded a Ritterkreuz by radio three days earlier, scuttled U-66. In the next three hours, Abel fished out and captured thirty-one more Germans, including Ritterkreuz holder Olschewski, but not Seehausen or his two British POWs. Altogether Abel captured and turned over to Block Island thirty-six Germans; twenty-four Germans perished.

  Apart from the U-801, which as related was sunk by the Block Island group, in late February and during the month of March, five other Type IXs sailed to Freetown and the Gulf of Guinea. None sank a ship. Three were lost.

  The veteran IXC U-515, commanded by the most highly decorated skipper still in Atlantic combat, Werner Henke, age thirty-five, who wore the Ritterkreuz with Oak Leaves, departed France on March 30. In addition to Naxos, the U-515 was equipped with one of the first of the Hohentwiel search radars.* On that same day, the Guadalcanal hunter-killer group, commanded by Daniel V. Gallery, sailed from Casablanca to hunt down U-tankers and their customers west of the Cape Verde Islands.

  Upon arrival in a likely area at sunset on April 8, Gallery launched four night-flying Avengers. Patrolling under a full moon, one of the pilots found U-515 on the surface but his alarm was not heard in the hunter-killer group. After recovering these aircraft and learning of the contact, Gallery launched other Avengers and sent two of his five destroyer escorts, Pope and Chatelain, commanded by Edwin H. Headland, Jr., and James L. Foley, respectively, to chase down a possible radar contact. Believing they got sonar contacts, the ships dropped depth charges. When Pope reported seeing an oil slick rise to the surface, Gallery sent Avengers and two more destroyer escorts, Pillsbury and Flaherty, to the scene. Two Avengers positively sighted U-515 and dropped depth charges, the second in the face of flak. None of these attacks caused any noteworthy damage to U-515, but Henke, who dived, was caught in a net he could not escape.

  After dawn on April 9—Easter Sunday—Dan Gallery initiated a dogged hunt. When Henke surfaced warily to charge batteries and air the boat, an Avenger, piloted by Douglas W. Brooks, dived to attack. Henke’s automatic, rapid-fire 37mm flak gun jammed at the crucial moment, and Brooks dropped depth charges and forced Henke to dive deep (787 feet), by which time Guadalcanal and her screen were merely fifteen miles distant. Three of these warships, Flaherty, Pillsbury, and Pope, and other aircraft, closed rapidly on the scene and commenced a persistent and effective attack on U-515 that went on for seven hours that Easter day.

  The close explosions eventually caused flooding in the after torpedo compartment that could not be stanched. Henke abandoned and sealed off that area, but the weight of the flooding aft pulled the bow up at a steep angle of thirty degrees. Henke attempted to decrease the angle by sending crew to the forward torpedo compartment, blowing tanks, and sp
eeding up, but these measures failed and U-515 slid down backward to about 656 feet. There U-515 went out of control and shot to the surface, stern first, with a down angle of 45 degrees.

  When U-515 popped up very close by, Chatelain and Flaherty opened fire with all guns that would bear, sweeping the U-boat’s deck clean of men. In addition, Chatelain shot seven more shallow-set depth charges from her K guns and Flaherty shot a torpedo. The torpedo missed U-515 and continued on toward the approaching Pillsbury. Astonishingly, an alert pilot saw the danger and sank the torpedo with machine-gun fire. He and other Wildcat and Avenger pilots then attacked U-515 with machine guns and rockets. Finally, in mid-afternoon, Henke ordered abandon ship and scuttled. Sixteen Germans died; the destroyer escorts recovered Henke and forty-three others and turned them over to Guadalcanal.

  In his colorful memoir of the U-boat war, Gallery asserted that he pressured Henke into signing a statement guaranteeing that he, Henke, would willingly give truthful information provided Gallery did not turn him and his crew over to the British authorities who had supposedly vowed to court-martial him and them for the “atrocity” of sinking the troopship/liner Ceramic (on December 7, 1942). In his book on the U-boat war,* the German journalist Hans Herlin, who interviewed three of Henke’s officers, disputed this assertion. However, Henke’s American biographer, Timothy P. Mulligan, has located in the National Archives and authenticated the document signed by Henke, as well as a similar document signed by forty enlisted men of U-515.

  The Guadalcanal landed Henke and his men in Norfolk on April 26. After six days in an Army processing center, Camp Allen, American authorities divided the Germans into two groups. Henke and eighteen men went to Fort Hunt, an elaborate top-secret Army-Navy interrogation center near Mount Vernon about seventeen miles south of Washington, D.C.† The other twenty-five men went to Fort George C. Meade nearby in Maryland for onward transfer to POW camps at Papago, Arizona, and elsewhere.