Britain began the war with a merchant fleet—soon to be christened by Winston Churchill, in one of his flashes of linguistic inspiration, the Merchant Navy—of 3,000 ships, totalling 17.5 million gross registered tons. By the end of 1941, when the United States (with 1,400 ships of 8.5 million gross tons) entered the war, the Merchant Navy had lost 1,124 ships, including neutrals sailing with British war cargoes, totalling 5.3 million gross tons. However, 483 ships had been acquired from German-occupied Norway, Greece and Holland, and another 137 requisitioned as prizes from the enemy, totalling four million gross tons. British yards meanwhile built ships of about two million gross tons, with the result that between September 1939 and December 1941, the month of Pearl Harbor, the Merchant Navy effectively increased in size to 3,600 ships totalling 20.7 million gross tons. In retrospect it seems astonishing that owners, to say nothing of their employed crews, were prepared to acquiesce in the chartering of their ships into the Battle of the Atlantic. Their readiness to take the risk, commercially and personally, can be explained only by what Clay Blair has demonstrated to be the relatively low rate of loss.25
In what may be characterised crudely as a personal struggle between Churchill and Dönitz, Churchill can thus be seen to have been outbuilding and outchartering Dönitz in the period September 1939 to December 1941. Measured in terms of tonnage sunk, Dönitz’s preferred index of success, Britain was keeping ahead. After 7 December 1941, when the might of United States industry was thrown unequivocally into the balance, the Anglo-American alliance drew unchallengeably away. At the forefront of the tonnage struggle was the dynamic American industrialist Henry Kaiser, a civil engineer who had built the Hoover Dam and other major works during Roosevelt’s programme of reconstruction after 1932. Requested to devote his time-and-motion techniques to ship construction, Kaiser designed a standardised merchant ship, the Liberty ship, modelled on a British general-purpose freighter, and built shipyards on the west and east coasts that could turn it out, partly by prefabrication, in as little as four days. The average was forty-two days and, by the Kaiser method, 2,710 were built during the war. The number included the superior Victory ship, which could do eighteen as against eleven knots. Kaiser also built the T2 and superior T3 tankers and numbers of escort carriers. When the output of the Kaiser shipyards is set against U-boat sinkings in the North Atlantic, 1,006 ships in 1942 but only 31 in 1944, it becomes clear that Dönitz’s hope of winning a tonnage war was quite misplaced. As had not been the case in the First World War, Germany’s enemies could outbuild the U-boat’s ability to sink. However hard Dönitz drove his captains, statistics, by mid-1943, had turned decisively against them.26