Tom Rider's Reviews

Michael Gannon. Black May; The Epic Story of the Allies’ Defeat of the German U-boats in May 1943. Naval Institute Press, Paper. 2010.

In May of 1943 a battle ranged at sea between a pact of German Unterseeboot, U-boats, and Allied warships, accompanying a convoy of 43 merchantmen traveling west in the North Atlantic from Britain. Michael Gannon believes this naval engagement to have been a turning point in the war-long struggle to end the U-boat threat to the North Atlantic. He has adopted the German name for this battle, Black May.

The shipping of vital supplies from the Western Hemisphere for the British war effort had been organized into convoys with escorts. These naval escorts – destroyers, destroyer escorts, and corvettes – were designed and redesigned for anti-submarine warfare. With the exception of a gap in mid-ocean, Allied convoys were also escorted by land-based planes, mostly Liberator bombers. Escort carriers were added midway through the war.

The Germans had had a marked superiority in submarine warfare when the war broke out in 1939, and the result was an enormous toll of merchant ships and their crews. But the Allies organized the convoy system and continued to improve radar and sonar technologies that assisted warships in fighting off U-boat attacks. The Germans countered by grouping their U-boats into ‘wolf packs’ of a half dozen or so ships. But even by 1943 it was clear, Gannon contends, that the Germans were loosing, measured by the ratio of merchant tonnage sunk to U-boats lost.

Over the years much as been said about the British access to encrypted German radio traffic. As Gannon points out, however, there were time delays of from 24 to 40 hours between the interception and decryption of German radio signals, which hampered pinpointing the location of German U-boats. Still British intelligence knew which convoys were threatened by the proximity of U-boats, allowing better use of the escort ships.

U-boat duty was the most deadly of the various German military services. And the specter of being sent to the bottom in a U-boat hit by a depth charge should have discouraged German boys from volunteering. However, the service was an elite force, U-boat sailors enjoyed better pay and food, they were more likely to win metals, and the high tech character of the U-boat’s appealed to many.

They were well-trained for their duty and aware of the fact that one sailor not doing his job could sink the U-boat with all hands on board. Gannon reports the grim site of bubbles, then an oil slick, and then debris that marked the destruction of a U-boat. Yet Gannon contends that there was no evidence that German U-boat crews became demoralized. Even in the last months of the war, a much depleted U-boat force was being sent out on missions.

Then there was the fact that no one wanted to serve on the Russian front.

The U-boat effort to disrupt British shipping was also deadly for the British merchant marine. Of the 185,000 merchant seamen who served during the war, almost 33,000 were killed, a 17% loss. In contrast the Royal navy lost 9%, and the British army, 6%. Sadly, Gannon notes, their deaths are rarely commemorated.

U-boats could travel much faster using diesel fuel if surfaced, and their torpedo firing was much more accurate. So the Allied strategy was to keep the German U-boat submerged when attacking. They had to surface periodically to recharge their batteries and air out the ship. Surfaced they were more vulnerable to detection by aircraft. But on the other hand, they could defend themselves from air attack with their deck guns. Surfacing at night was a good solution until the British equipped their Liberator bombers with search lights.

Gannon contends that Black May convinced the German naval command that further U-boat activity in the North Atlantic was futile. The ships were transferred to disrupt shipping on the West African, Caribbean, and Brazilian coasts and Allied troop transports in the Mediterranean.

Mike Gannon is a local author and Emeritus Professor of History, UF. He has managed to infuse his narrative with interesting and vital details without bogging the reader down with the minutiae of military history.