by Kahn, David
Among the convoys that twisted and turned in response to the section’s orders was SC 127.
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SC 127
FOR HOURS ON FRIDAY, APRIL 16, 1943, A FEW DOZEN SHIPS furrowed the waters of the 10-mile channel to the sea from the bustling port of Halifax, Nova Scotia. They steamed between the red sand cliffs to starboard and the white granite hills to port that guarded the narrow entrance. Out on the ocean they arranged themselves into a convoy’s customary broad-fronted formation. Convoy SC 127 had been born.
Its fifty-four ships, plus three that joined later from St. John’s, were taking to Britain material both for the British war economy and for the eventual invasion of western Europe. The Fort Howe and the Picotee and the Belgian Sailor all carried tanks and grain. The Keilhaven and the Mimosa carried steel and lumber. No fewer than nine ships had explosives in their holds. Others were bringing over fuel oil, lubricating oil, sugar, and phosphates. The commodore’s ship, the Empire Franklin, carried general cargo. Most were headed for Loch Ewe in northern Scotland; others for Glasgow, Belfast, Liverpool, Manchester, London.
The Atlantic into which they were heading was the theater of a battle in which the Germans seemed to be approaching victory. In 1942, the Germans had sunk more tonnage than the Allies had built. The daily average of U-boats in the Atlantic and Arctic rose from 92 in January 1943 to 111 in April. The number of Allied ships sunk almost doubled month by month: 29 in January, 50 in February, 95 in March. Indeed, March saw the greatest convoy battle of the war, when 45 submarines swarmed around convoys SC 122 and HX 229, sending dozens of ships to the bottom.
And this was happening at a time when, though it had become clear that Britain would not starve and her factories would not close down, severe shortages persisted. Stocks of food and goods had not yet recovered from having been drawn down during the previous year. Imports to Britain had in January reached their lowest level of the war. Beef and veal imports had begun their 1943 slide to 310,000 tons, about half the yearly prewar average. Rationing continued. Each individual was entitled to two ounces of tea per week and four ounces of bacon and ham. The cheese ration had been halved in February from the generous eight ounces of 1942.
The Ministry of Food sought to reduce the amount of wheat brought in, on which Britain was especially dependent: in 1939 she had produced 1,668,000 tons but had imported 8,519,000, The ministry considered raising the rate of extraction of flour from wheat from the customary average of 70 to 75 percent to 90 or 95 percent and diluting the flour with barley and oats, even though this would produce a darker, less palatable, and less digestible bread. But the barley could be obtained only by reducing beer production and closing the pubs two days a week. The committee in charge unanimously recoiled from this. It and the brewers finally agreed, however, that oats and dried potato bits would replace 10 percent of the barley used in brewing. The plan was put into effect, and 280,000 fewer tons of wheat had to be imported. Such were the contortions the British government went through to save shipping space.
At the same time, the euphoria of the Casablanca conference, at which Roosevelt and Churchill planned their next offensive and declared the war against the U-boats their priority, had all but worn off among the Allies’ military chiefs. They had come to see that the shipping situation was far worse than their earlier vague, optimistic impressions. The War Office miscalculated the number of vehicles and therefore the amount of shipping space per man needed for the North African invasion. Also the number of troops for that operation constantly increased, and, owing to the unexpected strength of the enemy opposition, the date when the buildup would be complete continually receded. Instead of the thirty ships a month that maintenance of the North African offensive had been thought to require, ninety-two sailed in February, seventy-five in March, and thirty-eight in April. Meanwhile, Turkey demanded 150,000 tons of grain that had been promised to keep her from raiding her traditional enemy, Russia. So tight was shipping that, far from being able to mount the operations against Japan that the Allies had grandly planned at Casablanca, Britain’s Ministry of War Transport was haggling over single ships on the routes to India and the Middle East. Famine loomed in Ceylon, where laborers were leaving the rubber plantations in search of food, and in East Africa, where Britain feared that the shortage of food would cause a breakdown in work at the main repair base of the Eastern Fleet in Mombasa. Ultimately, one and a half million people died of starvation or its diseases in British-ruled India.
All of this exerted extreme pressure on shipping, the shortage of which, the chief of the Imperial General Staff said, put “a stranglehold on all offensive operations.” And though details were probably not known to the codebreakers of Hut 8 or OP-20-G, they certainly felt the great and relentless need to save as many Allied ships as possible.
Convoy SC 127—codenamed for that series of convoys’ original starting place, Sydney, Cape Breton Island, Nova Scotia—was a slow convoy, one that could not maintain a speed of 10 knots; a fast convoy was one that could maintain that speed. But since no convoy could steam faster than its slowest ship, slow convoys averaged 7 knots, fast, 9. SC 127’s planned speed was 7.5 knots.
Because the British Isles are several hundred miles farther north than Nova Scotia, each convoy had to head north somewhere along its course. SC 127’s course, established nine days before sailing, called for it to start by sailing to Point F, at 46° 30′ north latitude, 46° 02′ west longitude, slightly north and well east of Halifax. From there, it would swing more to the north for a long leg to Point G, several hundred miles southeast of the tip of Greenland. Thence it would turn sharply eastward and then due east for the long run over the north of Ireland. If intelligence showed submarines lying along this route, it would be changed. And in fact, two days after it laid out the course, the Admiralty added some lettered points closer to Halifax, taking the convoy a bit south before it turned north.
The course changes were devised by Commander Richard Hall’s Trade Movements Section to avoid U-boat packs. The section based its plans on the reports of Winn’s Submarine Tracking Room, which depended heavily on the solutions put out by Hut 8 and OP-20-G. On April 16, when the convoy put to sea, the codebreakers were running three days behind in their solutions. But since this was the best available information, the two Submarine Tracking Rooms continued to issue their reports on the positions of enemy U-boats. The U.S. report for April 16 situated twenty to twenty-five U-boats in a rectangle bounded by 47° and 53° north and 44° to 37° west. The path of SC 127 that had been planned on April 7 ran right through this area. Hall would have to attend to that.
In the open sea SC 127 had formed itself into thirteen columns, of four or five ships, a pattern that reduced the number of shots a U-boat could get at the ships, compared to an arrangement with fewer but longer columns. The convoy’s size, fifty-four ships, reflected a lesson learned from operational research. This new field applied mathematics and science to military and naval problems. Analysis of aerial attacks on U-boats had shown, for example, that many submarines were escaping damage because the depth bombs exploded too deeply; when the setting was reduced, the kill rate went up. The Admiralty’s Operational Research Group had also calculated that a convoy twice as large as another one could be given the same protection with only one-third again as many escorts. In other words, a convoy of forty-eight ships could be as well protected with eight escort vessels as a convoy of twenty-four with six: in both cases the escort vessels would be 2 miles apart.
Five warships were to accompany SC 127, and by 1 P.M. on the day of sailing their leader, His Majesty’s Canadian Ship Dundas, was steaming on the port side of the convoy on a course of 122°. Escort was needed from the start because U-boats had audaciously sunk ships not only in the shadow of the Canadian coast but within the Gulf of St. Lawrence itself. The convoy’s commodore was a Royal Navy Reserve officer, W. van den Donker, master of the S.S. Empire Franklin. So SC 127 set out to bring her precious goods to Great Britain, heading s
outheast by east under a blue sky, on a calm sea, fanned by a gentle breeze from starboard, with visibility only 6 or 7 miles but with the barometer rising.
In Berlin, Hitler’s staff increasingly recognized that Nazi Germany needed to make greater efforts if she was to win this war. The devastating defeat at Stalingrad had impelled propaganda minister Joseph Goebbels to ask of a clapping, shouting audience at Berlin’s Sportpalast, “Do you want total war?” He got back a ringing “Ja!” The new armaments minister, Alfred Speer, increased war production. Authorities agreed that they had to cleanse the continent of subhumans; they put into effect the final solution of the Jewish people. And Dönitz, who on January 30 had been named commander in chief of the navy while retaining his post as commander of U-boats, and who now had more than four hundred submarines at his disposal, urged them to hurl themselves like wolves upon the enemy. On April 11, five days before SC 127 sailed, Dönitz told Hitler that his goal was to make the Allies bleed, to sink more ships than they could build.
Ahead of that convoy, perhaps half a dozen others were crossing the Atlantic in one direction or the other. To sink their ships Dönitz, had, on April 16, sixty-three boats operating in the Atlantic north of Halifax’s latitude of 44° 38′ north. One of the convoys U-Boat Command was concentrating on was SC 127’s predecessor, SC 126. A report by the B-Dienst told the command that four days previously SC 126 was located some 600 miles southeast of Cape Race, the southern tip of Newfoundland. The convoy had presumably passed the patrol line formed by a wolfpack codenamed TITMOUSE. But the submarines’ surface speed was superior to that of most convoys (a U-boat could cover 320 miles in 24 hours, an average convoy 240), so in hope of catching the convoy, Dönitz stretched TITMOUSE into a 650-mile northwest-southeast line with the U-boats moving roughly northeast. The next day, however, he abandoned hope of catching SC 126, saying that it might have slipped through the patrol line because of poor visibility.
U-Boat Command knew the rhythm of the convoys, and it knew that they sought to go around the U-boat concentrations. So on the seventeenth, with visibility expected to improve, Dönitz added more submarines to TITMOUSE and, supposing that the next convoys from Nova Scotia would go north to avoid wolfpacks, ordered it to take up a new patrol line. Farther west than the previous line, it was intended to catch the Allied ships as they sailed parallel to the Labrador coast.
The next day, however, two U-boats not in TITMOUSE spotted a pair of convoys so far to the south that the TITMOUSE submarines could not find them. Despite these sightings, U-Boat Command clung to its view that the next convoys would take the northern route. Perhaps reinforcing its belief was a report of a submarine’s sighting, to the north, a convoy that radio intelligence promptly identified as HX 234, from New York.
While U-Boat Command was mulling this over, SC 127 marched at about 7 knots along its predetermined course, passing Points C, D, and E as it headed first southeast out of Halifax and then east. Upon reaching E, at 6 P.M. Sunday, the eighteenth, it turned onto a course of 66°, or east-northeast. The barometer was now falling and the sky had clouded over, but the sea remained smooth and the air calm. Allied cryptanalysts had solved that day U-Boat Command’s long two-part message of the seventeenth establishing TITMOUSE, which ordered twenty-six submarines to form a patrol line as of 8 A.M. April 19, listing them in the order in which they were to take up position. Though the U-boats were identified only by their skippers’ names, their numbers were known. The German naval grid positions for the five points through which the line was to run were enciphered, but the cryptanalysts had determined the true meanings of many of the enciphered grid bigrams as well as of the disguised grid four-digit groups. They had learned, for example, that VD 0798 (the northwesternmost point) stood for AJ 5798, or 53° 45′ north, 46° 15′ west and that BU 8641 (the southeasternmost point) was BC 3641, or 49° 45′ north, 39° 55′ west. The solution revealed that the U-boats were to stay 15 miles apart and were to maintain radio silence “except for reports of tactical importance.” And, in a warning ominous to the Allies, it stated: “A convoy headed northeast is expected from that time on”—meaning from the time of the setting up of TITMOUSE.
The watch officers transmitted the first part of the solved, translated, and edited intercept to F-21, the Atlantic intelligence section of the headquarters of the U.S. Fleet, at 9:55 P.M. on Sunday, April 18, and the second part eight hours later, at 5:50 A.M. the next morning. Later on Monday Cominch—the commander in chief, U.S. Fleet—issued his submarine estimate for April 19. It named sightings, attacks, and direction-finding as sources; cryptanalysis was not cited, though much of the report was based on Enigma solutions. But Cominch blurred the precision that cryptanalysis provided, in part to conceal it as a source but in part because the U-boats might have moved since they received the intercepted orders and might have erred in their own positions and because Cominch did not want convoys and escorts not in the immediate area to relax their guard.
Part 3 of the estimate’s six geographical parts dealt with the North Atlantic. It began: “Twenty to thirty [U-boats] estimated patrolling general area 49-00 to 54-00 [north] and 38-00 to 48-00 [west] from light DF activity.” This was clearly based on the solution of the long message of April 17. It drew a rectangle based on the patrol line as its diagonal and fudged the number of U-boats. The rest of Part 3 gave details about other subs.
All day Monday, SC 127 followed the same northeast course in cloudy but calm weather. During the morning a patrolling Catalina seaplane made a welcome appearance overhead.
In Washington and Bletchley, the cryptanalysts hit a snag. They were unable to find any cribs, unable to create any usable menus, and so unable to recover the naval Enigma keys for that day. No messages enciphered with the keys of April 19 could be read. As a consequence, the U-boat situation report for Tuesday, April 20, merely repeated the most critical information from the nineteenth: the large rectangle containing the U-boats remained the same, though the number of U-boats reported in it came into focus: twenty-five. Other details changed slightly. For example, the “Four [in] general area 60-00 24-00” of the April 19 report became “About four within 150 miles of 59-00 from numerous DFs” in the April 20 report. This information was available to the Tenth Fleet’s Convoy and Routing Section, which digested it.
Germany’s naval codebreakers were more successful at that moment than the Allies’. They solved a message Tuesday that revealed that on Saturday convoy HX 234, then south of Cape Race, had been rerouted sharply to the north, probably to avoid a concentration of submarines. To counter this, U-Boat Command on Tuesday ordered TITMOUSE to move a second time: to the north and slightly west, to block the likely new route of HX 234.
The B-Dienst also solved an intercept dealing with SC 127. This convoy had been placidly plowing the calm western Atlantic on its east-northeast course, and continued to do so on Tuesday, when, at 9:55 A.M., a British escort relieved the Canadians. The German solution placed the convoy southeast of Cape Race at 5 P.M. Tuesday. “Since this position lies relatively far to the south,” U-Boat Command stated, “it is assumed that the convoy, contrary to earlier experience, will keep on the previously steered easterly course.” The command detached four boats from TITMOUSE to set up a short north-south patrol line, to be expanded by submarines coming from the east. The position of the line showed that the Germans expected SC 127 to steam south of the concentration of U-boats they knew the Allies knew about.
That Tuesday, April 20, Adolf Hitler celebrated his fifty-fourth birthday. Before and after it he received the leaders of his cobelligerents in Klessheim castle in Salzburg. On the battlefronts, little of note was happening. Army Group Africa, squeezed into a corner of Tunisia, struck out with a counterattack to throw British preparations for an assault off balance. In the air, the British bombed Stettin, a Baltic port, with 304 planes; the Soviets likewise attacked Tilsit, farther east. The Jews in the Warsaw ghetto were in the second day of their heroic uprising. In Germany, people were talking a
bout the discovery of the mass grave in Katyn of more than 10,000 Polish officers murdered by the Soviets. Some saw it as an example of what awaited the Germans if the Russians won the war; others said the Germans had no right to criticize since they had killed Jews and Poles in much greater numbers. Of the war situation, Germans said realistically that they were powerless in the air and that a German Dunkirk was approaching in Tunisia. Some wanted Hitler to show himself more, at least in newspaper photos and newsreels, to prove that his hair had not turned white. But any despair they felt was not translated into a slowdown at work: production of guns, planes, U-boats climbed.
In the United States, the baseball season opened. Since President Roosevelt was away—meeting the president of Mexico in Monterrey and pledging to beat the Axis so that the Good Neighbor policy could be extended throughout the world—the first ball was thrown out by Paul V. McNutt, the manpower commissioner. A crowd sprinkled with khaki and blue watched the Washington Senators beat the Philadelphia Athletics, 7–5. New York Mayor Fiorello La Guardia announced that 625 summonses had been served on retail food stores for violating food price ceilings and rationing regulations. In Tampa eight men and a cat came ashore in a life raft after their ship sank in the Gulf of Mexico.
And in the huge room of the Tenth Fleet’s Convoy and Routing Section in Washington, and in the staff rooms of the U-Boat Command in Berlin, men in blue uniforms pored over their vast lined charts of the North Atlantic, playing their deadly games of nautical chess, seeking, with the help of the totality of their knowledge, to outthink the other side and moving their vessels to destroy as many of the enemy’s or save as many of their own as possible. On April 20, the naval officers in Washington, including blond Lieutenant Commander Rollo N. Norgaard, who shared responsibility for SC 127, outthought—either by luck or by design—the officers in Berlin. They sent SC 127 not to the south of the big rectangle in the west central Atlantic that had held the TITMOUSE submarines, as U-Boat Command expected, but west and north of it. At 1539 hours Greenwich mean time, they released the first part and, five minutes later, the second part of a message to the warships escorting SC 127.
