Clay Blair has argued that in the early war years, Churchill and his colleagues constantly overestimated the U-boat menace, a mistake, Blair claims, that historians have faithfully reflected ever since. “In a word, the U-boat peril in World War II was and has been vastly overblown.” As a consequence, contemporary and subsequent impressions of the Battle of the Atlantic were “wildly distorted.” In 1939 Britain possessed more than five thousand merchant vessels of varying sizes; its fallen French, Dutch, Norwegian, and Belgian allies sailed perhaps another several hundred or so to British ports after June 1940. During the first eighteen months of battle, Germany possessed at any one time no more than a score of operational submarines of limited size, range, and offensive power. The Nazi submarine effort did not reach its apex until 1942–1943, by which time the United States was in the war and U.S. shipyards were beginning to turn out merchantmen at an astonishing rate in an incredibly short time. To argue, therefore, that the German David could slay the Allied Goliath was unrealistic. The very nature of the convoy system meant that when Dönitz’s assassins found one, losses could be appalling, but, as Blair maintains, the vast majority of Allied convoys during World War II were not found, instead sailing safely and undetected to their destinations.
But Blair himself is guilty of some serious distortions. Britain lost nearly one third of its prewar merchant marine (roughly sixteen hundred vessels) in the first eighteen months of the war, during a time when it was struggling to hold a worldwide empire that required maintaining its maritime resources on a global scale. And losses in the Atlantic were due to the balanced nature of the German assault against enemy shipping. Manageable as it might be by itself, the Nazi submarine threat became a frightful menace when combined, as it was, with airpower and surface raiders.
Moreover, the quantitative sinking of ships was only one measure—and not a particularly accurate one—of U-boat success. Qualitative sinkings were equally important. Although throughout the war Dönitz’s lads happily attacked any convoy found and any ships in that convoy, there is circumstantial evidence that oil tankers were, properly, the prime targets. By 1939 oil in its many guises had become the lifeblood of the advanced industrial world. Sink enough tankers, blow up their cargo or send it spilling in flaming bursts onto the sea, deprive Britain— and later Anglo-British forces in North Africa, Italy, and north-western Europe— of enough petroleum, oil, and lubricants, and the Allied war machine, on the ground and in the air, would come crunching to a halt, no matter whether the British public was hungry.
This strategy was invoked as soon as the United States entered the war and Dönitz could get his first five boats across the Atlantic. A disproportionate number of tankers sailing alone from the Venezuelan oil fields across the Caribbean, through the Straits of Florida, past the North Carolina Outer Banks, and on to New York for eventual dispatch to British destinations were destroyed by German U-boats during their passage up the U.S. East Coast. When the Americans at last got these invaluable vessels into proper convoys with decent air support, resourceful German skippers went after the convoys with a killer resolve. “Unmitigated disaster” befell TM(Trinidad-Mediterranean)-1 when this too lightly escorted convoy set sail from Port of Spain in January 1943 with nine good-size tankers filled with about thirty million gallons of fuel, “much of it high-octane aviation spirit” meant for the recently opened North African front. Spotted by U-522 shortly after departure and soon beset by a seven-boat wolf pack that overwhelmed the single destroyer and three corvettes in escort, TM-1 staggered across the central Atlantic in ever dwindling numbers, fighting for its life night and day. By the time the convoy reached Gibraltar on February 8, it had been whittled down to only two tankers. The seven others, comprising 56,453 gross tons and carrying nearly 22 million gallons of precious cargo, lay as shattered hulks at the bottom of the Atlantic, dispatched by Dönitz’s determined U-boat sailors.
While Karl Dönitz’s U-boats by themselves did not come anywhere near cutting the Allied lifeline to Britain, as it was so deeply feared in 1941 and 1942 that they might, close examination strongly suggests that the total German effort at sea and against British ports by plane, mine, and surface warship as well as U-boat between 1939 and 1942 did indeed come as close to victory as those at the time feared. Moreover, the German effort proved extraordinarily disruptive to British domestic and economic life, with catastrophic consequences for the future international power and status of the nation and its empire.
All this was accomplished under terrible political constraint, for in fact Adolf Hitler never really settled in his mind whether he wished to destroy England or to embrace it. Indeed, he never indicated clearly to anyone exactly what his strategic vision was, or how far it extended. His most bloodthirsty public threats were often followed by quiet private reservations. Dönitz wanted to wage a pitiless trade war with his U-boats against Britain to starve it and bring it to its knees—and to the peace table. Erich Raeder stood right behind him, poised to use the small surface navy to the same effect. The führer’s Directive No. 9 of November 29, 1939, reflected this policy, stating that “destruction” of the enemy’s economy was the quickest way to victory. Once war came, Hitler made the U-boat an immediate priority, though it would take months if not years to translate into a plethora of wolf packs at sea.
Yet as late as January 1941, Hitler indicated to the Wehrmacht leadership that although the war would be prosecuted with vigor both in the air and at sea, he was “still ready to negotiate peace with Britain.” Two months later he reversed himself, approving Raeder’s insistence upon “a concentrated single-minded operation by U-boats and the Luftwaffe against British maritime transport capacity.” He reversed himself again the following July as tensions and sinkings rose in the Atlantic following the U.S. occupation of Iceland. The Russian campaign seemed to be going well, and Hitler said that he was “most anxious to postpone the United States entry into the war for another one or two months.” Perhaps the entire U-boat campaign in the North Atlantic should be shut down for a time. Opportunities to deal with the Americans could be seized once the eastern war was wrapped up. The following October, just weeks before Pearl Harbor, with incidents in the Atlantic now threatening overt and immediate U.S. intervention, Hitler made the remarkable assertion to the chief of staff of the Naval War Staff, Vice Admiral Kurt Fricke, that he was “even now ready at any time . . . to conclude peace with Britain, as the European space which Germany has secured for itself through the conduct of the war so far is sufficient for the future of the German people.” In fact, Hitler had already lost the war in the East and thus the war in general. His last faint opportunity to defeat the entire Red Army had disappeared in August. But with advance elements of the Wehrmacht continuing to slip and slide toward Moscow through the late-autumn rains and sleet of the Russian steppe, neither he nor anyone else at the time could envisage such a thing.
Political constraints on a successful trade campaign were nearly matched by technological constraints. It is well to recall how perfect a metaphor German submarine-design and -construction programs were for the entire forced-draft Nazi rearmament program of the mid- and late thirties. Born clandestinely in foreign yards, the U-boat program after 1933 was the frequent victim of a command economy struggling to create a vast war machine in a few brief years from a limited industrial and resource base. Corners invariably had to be cut, and ruthless priorities had to be imposed by men like Hermann Göring who were both inexperienced and essentially uninterested in the subtleties and complexities of military buildup. Moreover, that buildup was always subject to political assumptions and imperatives. Prior to mid-1938, Hitler and his senior military people assumed that, with the Anglo-German naval treaty in hand, France and the Soviet Union would be Germany’s chief enemies in any future war. U-boat construction was oriented in that direction; small 500-ton vessels were built, suitable for operations along the shores of the Baltic and the French Atlantic coast, together with a handful of Type VII submarines somewhat larger than the conventional U-boat design of 1914–1918 in order to undertake distant operations against maritime trade around distant French colonies. Moreover, “substantial developments” had been achieved in overall U-boat capabilities: “better torpedoes with bubble-less ejection, trackless and with non-contact pistols; the ability to lay mines from all U-boats, to transmit and receive signals both surfaced and submerged, greater diving depths, and increased power of resistance through welded pressure hulls,” according to one U-boat skipper in an essay written for the British Admiralty in 1945.