A Game of Birds and Wolves: The Ingenious Young Women Whose Secret Board Game Helped Win World War II

by Simon Parkin

support group consisting of five warships to ‘proceed at best speed’ to reinforce the exposed convoy. It would, however, be two days before these ships could reach ONS.5’s position.

At 18:00 on 3rd May 1943, BdU signalled to the wolfpacks a stern command that made Doenitz’s expectations clear: ‘DO NOT HOLD BACK. SOMETHING CAN AND MUST BE ACHIEVED WITH 31 BOATS.’

The operation, which had convinced Sir Percy Noble of the value of WATU, required various triangular search patterns to be performed at precise sweep speeds and time durations, and was designed to flush out any U-boats sitting within the convoy lanes. That night, Sherwood performed a half-Raspberry, a slightly modified version of the manoeuvre that held a few escorts in place to survey the sea for any signs of U-boats illuminated by the star shells fired into the sky by the participating ships. The ploy worked magnificently. Various U-boats were located, enabling a barrage of depth charges to fend off the attackers.

In the final tally, one U-boat had been lost for every 2.6 merchant ships.9 Doenitz ordered the remnants of the wolfpacks to retreat. He later stated that he ‘regarded this convoy battle as a defeat’. This was an understatement. The Battle of Birds and Wolves would come to be known by the Germans as Die Katastrophe am ONS.5.

Together with the cutter Sennen, the two ships executed the WATU-coined manoeuvre Observant. Sennen dropped a pattern of ten depth charges, at least one of which punctured the hull of U-954, whose crew included Lieutenant Peter Doenitz, the grand admiral’s youngest son. There were no survivors.

Two months later, in July 1943, the tonnage of Allied ships launched, principally from American shipyards, finally overtook the figures of tonnage sunk. Doenitz, whose stated aim had always been to sink more ships than the enemy could build (‘a continual bloodletting which must cause even the strongest body to bleed to death’,22 as he described it), and who avidly studied the monthly statistics kept by his staff,23 had lost. The combination of WATU-developed tactics, the newly minted support groups and the closing of the air gap combined to make May 1943 the month in which the U-boats lost the Battle of the Atlantic, the war within a war. That month, which the Germans subsequently dubbed ‘Black May’, Doenitz lost forty-one U-boats. It was a decisive tally on this, the impersonal scoresheet of war. The grand admiral of the German navy, who never lost his first love for U-boats or the young men who crewed

them, ordered the withdrawal of wolfpacks from the Atlantic battlefield. It was, he urged, merely a temporary and ‘partial’ change of operations area. Four months later the US admiral Ernest King downgraded the U-boats to the category of ‘problem’ rather than ‘menace’.24 The so-called tonnage war was finished, and with it, in most ways that mattered, the Battle of the Atlantic.

Then in late May the Allies also confirmed that BdU had cracked the British naval cypher, and had been intercepting communications with convoys at sea for months. This had enabled Doenitz and his men to intelligently guide the wolfpacks toward convoys. Realising the exposure, the US and British navies switched to a newer code, known as Naval Cypher No. 5–once again blinding Doenitz and the U-boats.

Two-thousand-six-hundred-and-three merchant ships and 175 of the convoys’ escorting naval vessels were sunk in the Battle of the Atlantic, the longest continuous military campaign in the Second World War. More than 30,000 merchant seamen, and more than 6,000 Royal Navy sailors died in the Atlantic during the war, many following attacks by U-boats.4