by Clay Blair
This episode led to a testy exchange of messages between Admiral King and First Sea Lord Cunningham. To protect to the extent possible the secret of having broken Enigma, the British again urged that the Americans refrain from attacking U-boats meeting to refuel. Block Island had intensified British worries inasmuch as she was operating in a U-boat rendezvous area, after the Germans had made the emergency modifications to Enigma keys (first letter of certain crewmen’s first name, last name, plus home address, and so on) a fact that, if known to U-boat Control, might speed up its plan to make the forecasted “major changes” in Enigma.
King responded that the Americans would not conform to British requests. The kills of Block Island had not compromised the Allied codebreakers. The Block Island hunter-killer group was operating in an area derived from Enigma decrypts before the modifications had been made. Moreover, the Americans had been operating “jeep”-carrier groups in that area for quite some time. The absence of the hunter-killer groups at the refueling rendezvous might raise more suspicions among the Germans than their presence. The German suspicions that Enigma was compromised had not been caused by Block Island, but most likely by the British in routing convoys to evade U-boats and by sinking Charlotte Schliemann and Brake.
The next boat to sail to the Far East in February was the new IXC40 U-843, commanded by Oskar Herwartz, age twenty-nine, who left Lorient on February 19. She, too, was to refuel from Bruno Studt’s XIV tanker U-488 that sailed four days later. The two boats traveled south separately. On March 6 and 12, Herwartz in U-843 stopped and searched neutral freighters, let them go, and then continued south. He met the XIV U-488 west of the Cape Verde Islands on March 24 and topped off his fuel tanks, continuing southward.
As related, on April 4, he met Spahr in the homebound U-cruiser U-178 to give him new Enigma keys. In the midst of the exchange, a B-24 of U.S. Navy Squadron VB 107 from Ascension Island, doubtless aided by Enigma decrypts, strafed U-178 but dropped no bombs. In the South Atlantic on April 8, Herwartz found and sank the lone 8,300-ton British freighter Nebraska. Three days later, April 10, another B-24 of U.S. Navy Squadron VB 107, piloted by Edward A. Krug, attacked the boat, knocking out both stern tubes. As a result, Control directed Herwartz to cancel intended operations off Cape Town and refuel from a Japanese submarine in the Indian Ocean. He did, and arrived in Jakarta on June 11, completing an arduous voyage of 114 days.
The next boat to sail in February was the new IXD2 cruiser U-851, commanded by Hannes Weingaertner, age thirty-five, who sailed from Kiel on February 26. He carried cargo, including 1,878 bottles of mercury and five hundred U-boat batteries. In compliance with ill-advised orders from Control, on March 27 Weingaertner broadcast a weather report from the North Atlantic for the benefit of the Luftwaffe and the anti-invasion forces in France. Nothing further was ever heard from him. In view of his large fuel supply, it was assumed at first that U-851 reached the Indian Ocean, but on June 30, the 126th day after departure, Control declared the boat lost to “unknown causes.” No trace of U-851 has ever been found. She sank no ships on this patrol.
The last boat to sail in February was the IXC40 U-537, commanded by Peter Schrewe, which left Lorient on February 29. Six days out from France, on March 5, an unidentified Allied aircraft attacked the boat. The damage was so severe that Schrewe was forced to abort. He reached Lorient on March 6, and was under repair for the next twenty days.
Four boats sailed from France to the Far East in March.
First away was the veteran IXD2 cruiser U-181, commanded by a new skipper but a pioneer submariner, Kurt Freiwald, age thirty-eight, crew of 1925, who left La Pallice on March 16. In the middle of the South Atlantic on May 1, Freiwald sank his first ship, the lone 5,300-ton British freighter Janeta. Patrolling the Indian Ocean in June and July, U-181 got three more freighters: the 7,100-ton Dutch Garnet, the 7,100-ton British Tanda, and the 5,300-ton British King Frederick. He arrived in Penang on August 8, completing a patrol of 146 days.
Next sailed the veteran IXD2 cruiser U-196, still commanded by Ritterkreuz holder Eitel-Friedrich Kentrat, age thirty-seven, crew of 1928, who left La Pallice on March 16. After reaching the Indian Ocean, Kentrat sank one ship in the Arabian Sea, the 5,500-ton British freighter Shahzada. He reached Penang on August 10, completing a voyage of 149 days. Thereafter he left the boat to command a small German naval unit in Japan.
The IXC40 U-537, commanded by Peter Schrewe, resailed from Lorient on March 25. He refueled in the Atlantic Ocean from the XIV tanker U-488 on April 17 and proceeded to the Indian Ocean. Schrewe claimed sinking a destroyer off Ceylon on July 8, but the claim could not be confirmed. Inasmuch as Allied aircraft and submarines had mined the approaches to Penang and British submarines lurked off the port continuously, U-boat Control established new bases in Java. Schrewe arrived in Jakarta on August 2, completing a voyage of 131 days.
The last boat to sail for the Far East in March was the gift from Hitler to Tojo, “Marco Polo II,” the new IXC40 U-1224, commanded by Kriegsmarine officer Georg Preuss, age twenty-seven, and redesignated RO-501. The boat sailed from Kiel on March 30 with a Japanese crew. Acting on information from Allied code-breakers, a hunter-killer group composed of Bogue and five new destroyer escorts searched for U-1224 west of the Cape Verde Islands. At dusk on May 13, the destroyer escort Francis M. Robinson, commanded by John E. Johansen, got a sonar contact and attacked with depth charges and Hedgehogs. These apparently destroyed U-1224. No trace of her or Preuss or her Japanese crew was ever found.*
Four more new U-cruisers sailed to the Far East in April. None, of course, required refueling.
First out was the IXD2 U-859, commanded by Johann Jebsen, age twenty-seven. Fitted with a snort, she sailed from Kiel to Penang on April 4. While passing through the North Atlantic on April 26, Jebsen came upon several stragglers from Slow Convoy 157 and sank the 6,300-ton Panamanian freighter Colin, as related. He reported the sinking to Control and escaped detection by the swarms of Allied ASW forces in the area.
Jebsen rounded the Cape of Good Hope into the Indian Ocean in late June. In early July, an unidentified British Catalina attacked U-859 southeast of Durban with machine-gun fire and depth charges, inflicting severe damage. One seaman was killed and three men were wounded, the second watch officer seriously. The explosions holed a fuel tank, smashed the snort elevating gear, and unseated two diesel engines or motors. Jebsen escaped the ensuing Allied ASW hunt, made repairs, and proceeded north to the mouth of the Gulf of Aden, where in late August he sank two freighters, the 7,200-ton American Liberty ship John Berry and the 7,400-ton British Troilus.
Jebsen then set a course for Penang, arriving off that port on September 23, the 173rd day of the patrol. The British submarine Trenchant, commanded by Arthur R. Hezlet, intercepted the U-boat as she was preparing to enter port with a Japanese escort. Hezlet fired three stern torpedoes at U-859. One hit the U-boat amidships and sank her. Trenchant rescued the junior engineer Horst Klatt, age twenty-two (who had survived the accidental sinking of the VII U-612 in the Baltic), and ten enlisted men. The Japanese escorts rescued eight other enlisted men.†
Next to sail was the new IXD2 U-860, commanded by Paul Büchel, age thirty-six, crew of 1925, who sailed from Kiel on April 11. On June 9, while in the middle of the South Atlantic, Büchel reported to U-boat Control his position and the fact that he had lost two men overboard in the storm-tossed North Atlantic. Allied forces DFed this transmission, which confirmed Enigma tracking intelligence, and a hunter-killer group built around the American “jeep” carrier Solomons, newly arrived in the South Atlantic, commenced a search for U-860. On the morning of June 15, Avenger pilot George E. Edwards, Jr., found, reported, and attacked U-860 four times in the face of intense flak, but his report was not discovered in the hunter-killer group until later. On the fourth run, Büchel’s gunners shot down the Avenger. No trace of Edwards or his crew was ever found.
Toward sunset, another Avenger pilot, Howard M. Avery, found U-860 on the surfa
ce. His contact report brought in two Wildcats and another Avenger. All four aircraft attacked U-860 three times with rockets, machine guns, and depth charges. A depth charge from the low-flying Avenger exploded on the forward deck of the U-boat and engulfed the aircraft in flames. Neither the pilot, William F. Chamberlain, nor his crew was found.
Fatally damaged, U-860 sank. Six hours later, the destroyer escorts Herzog and Straub of Solomons’s screen, searching in darkness, fished Büchel, his first watch officer Otto Wilhelm Carls, and nineteen other Germans from the water. One dead German was buried at sea. Solomons landed the other survivors in Recife, Brazil.
The third U-cruiser to sail in April was the veteran IXD2 U-198. Commanded by a new skipper, Burkhard Heusinger von Waldegg, age twenty-three, the boat left La Pallice on April 20. He was assigned to give Lüdden in the inbound U-188 Enigma keys on May 14, but the rendezvous failed, probably because Lüdden’s radios were out of commission. Seven days later, an Allied hunter-killer group detected and chased the U-198 but she got away clean. Off Cape Town on June 16, von Waldegg sank the 3,300-ton South African freighter Columbine. After rounding the Cape of Good Hope into the Indian Ocean, two Venturas based in South Africa attacked U-198 with depth charges on July 6, breaking loose a number of rubber dinghies stored under the topside decking. Cruising north in the Mozambique Channel, von Waldegg sank three British freighters: the 5,100-ton Director, the 7,300-ton Empire City, and the 7,200-ton Empire Day. Several other attacks on Allied shipping, including the ex-American Coast Guard cutter Saranac, renamed Banff by the Royal Navy, and the Australian motorship Lismore, failed.
On August 12, an Avenger from a British hunter-killer group built around the new American-built British “jeep” carriers Begum and Shah found and attacked U-198 with depth charges. A British Catalina took up the tracking and homed in three ships of the screen: the British frigates Findhorn and Parret and the Indian sloop Godavari. Findhorn and Godavari teamed up to destroy U-198 with depth charges and Hedgehogs. There were no survivors. The sixty-seven dead included the captain of Empire Day, whom Waldegg had taken prisoner.
The last U-cruiser to sail in April was the new IXD2 U-861, commanded by Jürgen Oesten, age thirty-one, which sailed from Kiel on April 20. Earlier in the war, Oesten had won a Ritterkreuz for sinking six ships while commanding the duck U-61 and ten ships and a hit on the British battleship Malaya while commanding the IXB U-106. Subsequently, he had served as a staff officer at U-boat Control and as a chief adviser for submarine operations in the Arctic.
Oesten patrolled to the Indian Ocean by way of Brazil. Off Rio de Janeiro on July 20, he sank the 1,700-ton Brazilian freighter/troopship Vital de Oliveira, which was carrying about two hundred soldiers to Europe. Oesten also attempted to sink her single, small escort with a T-5, but the escort fled. The Brazilians reported that 101 men perished in the sinking. Four days later, Oesten sank the 7,200-ton American Liberty grainship William Gaston. The U.S. Navy had diverted her to avoid U-861 but inadvertently put her exactly in Oesten’s crosshairs.
There were sixty-seven men on William Gaston, including a twenty-six-man Armed Guard crew. All got away in three lifeboats and one raft. Following a horrible night in heavy seas, shortly after noon on July 24, a U.S. Navy Mariner of Squadron VP 203 spotted the survivors. The pilot, Charles Snyder, gave the alarm. Other U.S. Navy Mariners and Catalinas responded, but could not land in the heavy seas. They stood watch until the squadron’s aviation tender Matagorda, based at Florianopolis, Brazil, arrived early on July 25 and rescued all sixty-seven survivors.*
After rounding the Cape of Good Hope on August 20, Oesten found and attacked a convoy, Durban North 68, composed of seven freighters, thinly escorted by three ASW trawlers. He claimed that he sank two ships for 16,465 tons from the convoy. Allied records confirmed the 7,500-ton British freighter Berwickshire but only damage to the 8,100-ton British tanker Daronia. Oesten sank a fourth confirmed ship on this patrol on September 5, the 5,700-ton Greek Toannis Fafalios. Thereafter, he proceeded to Penang, arriving on September 22, completing an exhausting summer voyage of 156 days. Of the four new U-cruisers sailing from Europe to the Far East in April, the U-861 was the only one to complete the voyage.
Delayed seven to eight months by the aforementioned accident in the Baltic and the installation of a snort, the new XIV “Milk Cow” tanker U-490, commanded by thirty-nine-year-old Wilhelm Gerlach, sailed from Norway to the Far East on May 6. In addition to oil, she carried a large cargo of supplies, spare parts, and electronics. She made her way slowly south, running submerged in daylight hours, sometimes charging batteries submerged by use of the snort.
The Americans put a hunter-killer group, built around the “jeep” carrier Croatan, commanded by John P. W. Vest, which sailed from Norfolk on June 3, on the trail of U-490. In the early hours of June 11, when U-490 got off a brief progress report to U-boat Control, the Croatan DFed the signal and Vest ordered the group to shape course to intercept her.
Shortly before 8:00 A.M. on June 11, Frost, one of the five destroyer escorts of the screen, got a sonar contact. The screen commander, Frank D. Giambattista in Frost, directed her skipper, John H. McWhorter, to attack. Frost fired her Hedgehog and got three hits. Another destroyer escort, Huse, commanded by James H. Batcheller, Jr., which hurried up to assist, threw over nine deep-set depth charges.
Caught unawares, Gerlach in U-490 took the boat, which had a reinforced pressure hull, down to nearly one thousand feet. Since this was deeper than Allied depth charges could reach, Gerlach was confident he could escape. But Giambattista, determined not to lose this U-boat, brought up another destroyer escort, Inch, commanded by David A. Tufts, and the three ships stuck with U-490 for over fifteen hours, carrying out twenty-five depth-charge attacks. Although these scores and scores of depth charges rattled the green German crew and the dozen-odd guinea pigs the ship’s doctor had brought along for experiments, they caused no serious damage. Fearful that Allied sonar would hear the squealing pigs, Gerlach ordered the doctor, Herbert Stubbendorff, to kill them.
To encourage U-490 to surface and attempt to escape in the dark, Giambattista at 11:00 P.M. put in motion a tactical trick. Inch and Frost pretended to give up the chase and exit to the north. Snowden, commanded by A. Jackson, Jr., which had relieved Huse, pretended to exit to the south. The trick worked. About thirty minutes after midnight on June 12, Gerlach surfaced U-490 between Frost and Snowden. Thereupon the three destroyer escorts illuminated the U-boat with star shells and searchlights and raked her with gunfire.
Realizing he was trapped, Gerlach signaled in English, “SOS please take our crew,” abandoned ship, and scuttled. The three warships continued to rake the valuable U-490 until she sank, stern first. Thereafter the American vessels rescued all sixty German crewmen. According to the American intelligence report, in return for a promise from group commander Vest that he would not turn them over to the British, the Germans signed a statement agreeing to “answer all ‘honorable questions.’ ” Among many other details, the prisoners revealed that German U-boats in the Baltic were experimenting with underwater refueling.
Although antiship operations by the twenty-four boats proceeding to and from the Far East in the first half of 1944 were in most cases secondary to the delivery of cargo, they nonetheless achieved some torpedo successes. The eight boats that set off from Penang for France (including U-178) sank fourteen ships for 77,500 tons. Lüdden in U-188 sank half of these for 42,500 tons. The sixteen boats that set off from Europe for the Far East sank nineteen ships for 114,369 tons. Altogether: thirty-three ships for 191,860 tons.*
The cost to the Germans was ruinous: the tankers Charlotte Schliemann and Brake and eleven submarines sunk. These included six U-cruisers;† the last remaining Type XIV “Milk Cow” tanker, U-490; the Type VIIF torpedo-supply boat U-1059; Hitler’s gift to Tojo, “Marco Polo II,” the IXC40 U-1224; and two Italian cargo submarines, U-IT22 and U-IT23. Of the approximately six hundred men serving on these eleven boats, 423 p
erished and 177 were captured by the Allies. Five boats bound from Penang to France were forced to abort. ‡
Of the twenty-four boats sailing to and from the Far East in this period, only eight (33 percent) reached their intended destinations. Two, U-178 and U-188, got to France with a combined total of about three hundred tons of rubber, tin, tungsten, quinine, and opium. Six§ got to the Far East, most loaded with supplies for the German U-boat base at Penang, including notably about sixty torpedoes and three U-boat propellers; and for the Japanese Navy, lead and mercury.
THE CODEBREAKERS
By April 1944, there were ninety-six four-rotor American bombes in continuous operation at the Nebraska Avenue facility in Washington, D.C. Two bombes had been combined to make a single “Double Unit #800 Bombe,” a monster electromechanical machine that was sixteen feet long, seven feet high, and four feet wide. The other ninety-four bombes were the “standard” Model 530s. Hundreds of programmers and Waves assigned to three eight-hour watches operated the machines nonstop. Scores of enlisted men maintained the bombes in working order; other technicians set up experimental adaptations that emerged from Howard Engstrom’s fecund Research Section.*
These American bombes produced about 1,400 naval Enigma decrypts a month, including all radio traffic to and from U-boat Control and the U-boat theater commanders and the flotilla commands as well as the U-boats at sea.† On April 24, Engstrom, Meader, and Wenger wrote that “the decryption of German naval traffic has been very successful during the past six months” (November 1943 through April 1944). They elaborated that during that period, each day “all units” [bombes] were first directed to produce the naval Enigma keys and when this had been accomplished, the bombes were used to solve “non-naval research problems carried out at the request of the British.” Nearly half (45 percent) of all American bombe running time had been devoted to British problems, mostly concerning German Army and Luftwaffe networks.