Black May

BLACK
MAY

MICHAEL
GANNON

To B
UZ
W
YETH

This May the situation was quite out of hand: as I was soon to learn, the number of boats that failed to return from patrol reached 41, more than one a day, and there was talk of “Black May.”

May was a very black month for the U-boats. Sinkings of U-boats probably averaged one a day.

We had lost the Battle of the Atlantic.

I
N THE FIRST DARK HOURS
of the first day of the forty-fifth month of the longest armed struggle of World War II—the Battle of the Atlantic—
134
submarines of the German underseas fleet (
U-Bootwaffe)
were at sea, of which
118
were on or proceeding to operational stations in the North Atlantic Ocean, where,
58
were already deployed in four
battle groups. Most of the U-boats, as they were called, had sortied from French bases on the Bay of Biscay, the remainder from bases on the Baltic Sea, from which they rounded the north of Scotland. It was the largest number assembled at sea to that date in the war, I May 1943. Steel-gray spectral presences, they made an ominous murmuring across the deep, as of the gathering of a host, on the eve of a titanic trial of strength. At issue was control of the ocean’s merchant shipping lanes. The enemy was Great Britain’s Royal Navy and Royal Air Force, helped by forces of the United States and Canada. Most of the U-boats were ordered to form patrol lines across the expected routes of warship-guarded transatlantic convoys of freighters and tankers that sailed between North America and the British Isles. Others watched for north-south coastwise convoys or for independently sailing vessels along the shores of Spain and West Africa, or for shipping inside the Mediterranean Sea.

Armed with the most recent types of destructive torpedoes, all the Atlantic boats were under the same general order from Grossadmiral Karl Dönitz, Commander-in-Chief of the German Navy (
Kriegsmarine)
and Flag Officer, U-Boats:
Angreifen! Ran! Versenken!
—Attack! Advance! Sink! Their purpose in the transatlantic sea lanes: destroy British and American vessels that, through their deliveries of food, fuel, ferrous and nonferrous metals, other raw materials, and finished weapons, were keeping Great Britain in the war, and making possible a future Allied cross-Channel invasion of German-occupied Europe. As April gave way to May 1943, the Allied defensive war against the U-boat was perceived by many in London and Washington, if not in Moscow, as the single most important campaign of World War II, for upon its outcome rested the success or failure of the Allies’ strategies in all other theaters of operation. This was so because victory in Western Europe depended on uninterrupted sea communications across the North Atlantic, which provided aid to the Soviet ally as well as to the British (although Arctic convoys to Murmansk and Archangel had been suspended since March because of the growing crisis in the Atlantic), and because the Allied strategic assumption was that the defeat of Germany ensured the defeat of Japan, but not the converse.

Put in the simplest terms, Admiral Dönitz and his U-boats were engaged in a tonnage battle (
Tonnageschlacht
) with Allied trade, that is, in a campaign to sink more British and American merchant ship tonnage than the Allies could replace with new construction. Dönitz and his staff had calculated in 1940 that in order to accomplish that attrition, his boats (with surface raiders, aircraft, and mines accounting for a small percentage of the total) would have to inflict a monthly loss rate of 700,000 Gross Register Tons (GRT). If successful, Britain’s armed forces, industries, and people would be strangled or starved into submission. The British had estimated that 600,000 would be enough to do them in. But so far, by either measure, Dönitz was not winning that battle. Operating during the first half of 1942 in poorly defended waters off the United States East and Gulf coasts and in the Caribbean Basin, the best that he had done was 125 ships for 584, 788 GRT, of which only 10 percent was convoyed, in May 1942; and 131 ships for 616, 904 GRT, of which only 12 percent was convoyed, in June 1942. The best that he had done where most of the merchant traffic was convoyed under warship and aircraft protection was 118 ships for an impressive (and record) 743, 321 GRT, in November 1942. The numbers fell off in the following three months.

Then, in the first twenty days of March 1943, his sharks had gone on another feeding frenzy, sinking seventy-two vessels, sixty of them in fourteen Royal Navy—protected convoys. Twenty-two of the ship losses came on 16–20 March during an attack by three U-boat groups code-named
Raubgraf
(Robber Baron), consisting of eight boats;
Stürmer
(Go-Getter), eighteen boats; and
Dränger
(Pusher), eleven boats, with several other independently operating boats, against three convergent transatlantic eastbound convoys identified by the Allies as SC.122, HX.229, and HX.229A, with a combined 125 merchant ships in orderly columns. The three convoy formations had been protected during their passage by nine destroyers, three frigates, four sloops, nine corvettes, and two cutters, and at various times by fifty-one Royal Air Force and Royal Canadian Air Force aircraft.
¹
German radio broadcasts called the engagement “the greatest convoy battle of all time,” based on the number and tonnage of ships claimed as sunk for the loss of only one
attacker (U-384).
²
Allied tonnage lost to U-boats in the month by 20 March amounted to 443, 951 GRT. Had sinkings continued at that same pace for the remainder of the month, which they did not, the tonnage harvested (688, 124 GRT) would have approached November’s record and would have exceeded the original British minimum calculated for a decisive
guerre de course.
The actual monthly total was 105 ships for 590, 234 GRT.
³
And more to the point, by spring 1943 neither number would have matched the minimum tonnage now required to keep pace with replacement construction from America’s unexpectedly productive ninety-nine shipyards. The bar on the high jump had been raised to 1.3 million GRT.

Still, the numbers for March, particularly the losses from SC.122 and HX.229—HX.229A was unharmed—were of a magnitude to set off alarm bells in the Anti-U-Boat Division of the Naval Staff at the British Admiralty at Whitehall, London, the district where many government departments are located and a term frequently used as a synonym for
Admiralty.
In language committed to writing well after the convoy disaster, one senses the consternation that reputedly swept certain corridors of Whitehall at the time. Though the convoy system had proved in two world wars to be the keystone of Britain’s trade protection, for the first time in the second war there were doubters. “It appeared possible,” the Anti-U-Boat Division reflected, “that we should not be able to continue [to regard] convoy as an effective system of defence.”
⁴
In a watershed expression, the Admiralty is alleged to have conceded, “The Germans never came so near to disrupting communication between the New World and the Old as in the first twenty days of March 1943.”
⁵
Captain Stephen W. Roskill, R.N. (Royal Navy), official historian of Royal Navy operations in World War II, stated in 1956: “Nor can one yet look back on that month without feeling something approaching horror over the losses we suffered.”
⁶

One could have countered that there was no need for these expressions, since American shipyards were producing such prodigious numbers of replacement hulls, new Allied “bottoms” had already exceeded in the preceding fall any destruction that the U-boats were then inflicting; further, that 90 percent of all ships in convoys attacked by U-boats
were getting through to port safely, even 82 percent of hard-hit SC.122/HX.229. Indeed, well-hidden in the bowels of the “Citadel,” a concrete blockhouse on the northwest corner of Whitehall, two relatively junior reserve officers held the contrary and optimistic view that U-boat fortunes were in constant and inevitable decline. A mere glance at the graphs that covered the walls of their Submarine Tracking Room of the Admiralty’s Operational Intelligence Centre (OIC) was enough to persuade Tracking Room director Temporary Commander Rodger Winn, R.N.V.R., Special Branch, and his deputy, Lieutenant Patrick Beesly, R.N.V.R., that most of the relevant numbers were going Britain’s way: shipping losses alongside replacements; U-boat groups alongside Allied escort vessels and aircraft; U-boat equipment alongside new Allied weapons and detection devices.
⁷

But if we may believe the official history, their careful optimism seems not to have passed persuasively up and across to the Anti-U-Boat Division, whose attention, we are led to believe, was focused on quite a different set of facts: (1) that the Germans had the largest U-boat strength yet seen in the Atlantic war; (2) that U-boat construction still exceeded casualties; (3) that 84 percent of the ships sunk in March were sunk while in protected convoy; and (4) that from an average of 39 percent of ships sunk in convoy during the second half of 1942, the average toll for the first quarter of 1943 had risen to a startling 75 percent.
⁸
Captain Roskill expressed the worry: “Where could the Admiralty turn if the convoy system had lost its effectiveness? They did not know; but they must have felt, though no one admitted it, that defeat then stared them in the face.”
⁹
Would the U-boats succeed at last in severing Britain’s lifeline and winning the Atlantic—perhaps the war?

Those fears, amply expressed in the official history written thirteen years later, were not discovered by this writer in any of the documentation from the immediate post-20 March period as far as January 1944. That includes the Most Secret minutes of the War Cabinet Anti-U-boat Warfare Committee (A.U. Committee), the highest deliberative body to be concerned with such matters. Those fears would seem to be overwrought at best and irrational at worst, assuming that they were
actually uttered by Admiralty authorities, as reported. Indeed, on 30 March, in a document prepared for the A.U. Committee, the First Sea Lord, Admiral of the Fleet Sir Dudley Pound, spoke with cautious optimism about anti-U-boat prospects in the months immediately ahead. For one thing, he told the Prime Minister and members of that body, the heavy winter weather, which had caused so many merchant ship stragglers from convoys and had hampered the Navy’s high-frequency direction-finding equipment (receivers and antennas that tracked radio transmission from U-boats), was moderating. Second, both Support Groups (destroyers and other warships detailed to reinforce the close escorts of threatened convoys at sea) and auxiliary aircraft carriers had been freed up from operations in the Mediterranean and in North Russian waters, and were now being redeployed in the North Atlantic convoy lanes. Third, and most important, a significant number of new land-based aircraft were becoming available for Atlantic escort patrol. Thus, from the First Sea Lord, no Admiralty hand-wringing here!

And His Lordship might well have added that while during 1942 the at-sea loss exchange rate was 45,000 tons of merchant shipping sunk per U-boat lost, during the first quarter of 1943 the rate had fallen to 28,000 tons per U-boat lost. Other restorative tonics could be found in the facts that during the same first quarter, 270 more merchant ships in convoy made safe and timely arrivals at their destinations than had done so during the last three months of 1942; more U-boats (19) had been sunk in February than in any previous month of the war, and even in woeful March the figures for new shipping construction exceeded sinkings by 300,000 tons. It would seem that the despondency theme voiced by certain members of the Naval Staff s Anti-U-Boat Division and repeated in the Admiralty’s official history as well as in much of the historical literature since 1956 did not represent the Admiralty’s position and at this date deserves to be consigned overside in a weighted bag.
¹⁰

To the question of where the Admiralty could turn if the convoy system had lost its effectiveness, the only answer had to be, there was
no
alternative, save independent sailing, which had proved so disastrous when tried earlier that only Karl Donitz would have been comfortable
with it now. From January to July 1942 nearly 400 independently routed vessels had been lost to U-boats off the East and Gulf coasts of the United States and in the Caribbean Basin. As late as October-December 1942, 101 independents (including stragglers) were sunk in all sea lanes, as compared with 87 ships in convoy. And the final tabulation of the Atlantic struggle of 1939–1945 would reveal that in the nineteen most productive single U-boat patrols of the war, the losses of independently sailing merchantmen were 79 percent of the total tons sunk.
¹¹
It should have been obvious by spring 1943 that a mass transfer of convoyed ships to the independent column would result in even higher losses, approaching the calamitous. It would have been equivalent, in fact, to giving the order, “Convoy is to scatter,” that First Sea Lord Admiral Sir Dudley Pound gave to the Arctic convoy PCX17 (Iceland to Murmansk) on 4 July 1942: of the thirty-four-ship convoy, twenty-four instantly created independents were sunk by German U-boats and aircraft. In sum, it remains hard to believe that sober minds in the upper reaches of the Admiralty seriously considered casting adrift the doctrine of convoy.

But if they did indeed waver, Their Lordships might have been emboldened in the faith did they know that statistical analyses done by the German Naval War Staff in Berlin at the same time revealed that the tonnage numbers credited to each U-boat per day at sea had been erratic and generally down since the preceding November. In that previously noted record month, the average per boat at sea number for the month was 329 GRT. In December it was 139. In January 1943 it was 129; in February 148; and in March 230.
¹²
By those numbers, for the U-Bootwaffe to meet the new tonnage minimum of 1.3 million GRT (of which Donitz may well have been unaware: the Naval Intelligence Division figure given him in 1943 was 900,000 GRT per month) it would have to place at sea no fewer than 433 boats—nearly three and a quarter times the current figure—which was not possible anytime soon given German shipyard production of 19 boats per month, which barely exceeded the monthly loss rate in combat.
¹³
For the present, a 1.3 million GRT achievement would have to come from greatly increased efficiency in each boat per sea-day, or from a collapse of British escort protection, or both. Neither seemed likely.