How to Get Convoys Safely Across the Atlantic
Thus was the stage set for Germany to fling into the Atlantic struggle the greatest possible strength. . . . It was plain to both sides that the U-boats and the convoy escorts would shortly be locked in a deadly, ruthless series of fights, in which no mercy would be expected and little shown. Nor would one battle, or a week’s or a month’s fighting, decide the issue. It would be decided by which side could endure the longer; by whether the stamina and strength of purpose of the crews of the Allied escort vessels and aircraft, watching and listening all the time for the hidden enemy, outlasted the will-power of the U-boat crews, lurking in the darkness or the depths, fearing the relentless tap of the asdic, the unseen eye of the radar and the crash of the depth charges. It depended on whether the men of the Merchant Navy, themselves almost powerless to defend their precious cargoes of fuel, munitions and food, could stand the strain of waiting day after day and night after night throughout the long, slow passages for the rending detonation of the torpedoes, which could send their ships to the bottom in a matter of seconds, or explode their cargoes in a searing sheet of flame from which there could be no escape. It was a battle between men, aided certainly by all the instruments and devices which science could provide, but still one that would be decided by the skill and endurance of men, and by the intensity of the moral purpose which inspired them. In all the long history of sea warfare there has been no parallel to this battle, whose field was thousands of square miles of ocean, and to which no limits in time or space could be set.
—S. W. Roskill, The War at Sea, 1939–1945
As Churchill and Roosevelt journeyed to and from Casablanca in January 1943, the weather in the North Atlantic had become as violent as any experienced sailor could remember. For much of December and January, huge storms at sea cramped naval and air activity. Merchant ships, pounded by giant waves, had heavy cargoes breaking loose and sliding around inside their hulls. Smaller warship escorts such as corvettes were tossed around like corks. Warships with heavier upperworks and gun turrets rolled from side to side. German U-boats, when they surfaced, could see nothing across the hundred-foot-high waves and were happy to submerge into quieter waters or to head south. Hundreds, perhaps thousands, of sailors were hurt, and not a few killed by accidents or washed overboard. In some extreme cases, the commander of a convoy was forced to order a return to base, or at least to send damaged ships back. General Sir Alan Brooke (later Viscount Alanbrooke) records in his diary that he, the other British Chiefs of Staff, and Churchill himself had their flight (or surface sailing) plans from London to Casablanca changed time and again.
The result, quite naturally, was that convoy activity upon the storm-whipped North Atlantic routes was much less than normal in these midwinter months. Quite separate from this physical interruption, there was a second and cheerier reason the regular convoy traffic fell away at this time. Operation Torch itself demanded a vast number of escorts to assist the occupation of the Vichy states of Morocco and Algeria—the Royal Navy contributed 160 warships of various types to it—and in consequence the Gibraltar, Sierra Leone, and Arctic convoys had to be temporarily suspended.1 Since ships carrying Allied troops, landing equipment, and immediate supplies were bound to get the highest level of naval protection, and the Axis was ill-prepared for the Operation Torch invasion because of its obsessions with the Eastern Front and Egypt, it is scarcely surprising that the invading forces met with little or no U-boat opposition on North African shores.
The other, understandable consequence was that Allied losses to enemy submarine attacks fell dramatically during midwinter. If there were fewer Atlantic convoys at sea in the first place, those that did sail, while battered by storms, were often protected by the same lousy weather conditions. Some were routed far to the north in a sort of great circle, trading physical damage by ice floes for distance from the wolf packs. The Admiralty’s monthly toll of shipping losses captured this dramatic decline well. For example, in November 1942 the Allies lost 119 merchant ships totaling 729,000 tons, and while many of these vessels were sunk in more distant waters, off South America, those supply lines were also part of an integrated effort aimed at sustaining and enhancing Anglo-American power in the British Isles. The sinking of British oil tankers coming from Trinidad would, as a consequence, hurt the buildup of the U.S. bomber groups in East Anglia; everything hung on command of the seas.
Because of the rough weather, U-boat sinkings in December and January fell to a mere 200,000 tons of Allied shipping, most of which also occurred on more southern routes (e.g., Trinidad to Gibraltar, to supply the Operation Torch armies). But the tallies for those months were exceptional, for the reasons explained above, and thus when the prime minister and president met at Casablanca they were under no illusion as to how serious the crisis over shipping losses had become. The Allied merchant fleets had lost a staggering 7.8 million tons in the course of 1942, almost 6.3 million of which had been sunk by that most formidable weapon, the U-boat. The amazing American mass production shipyards were still gearing up to full strength, but even their output in 1942 (around 7 million tons) meant that total available Allied shipping capacity had declined in absolute terms, and now had to compete with the even greater demands of the Pacific War. By early 1943, therefore, British imports were one-third less than those in 1939, and U.S. Army trucks and box-bound aircraft now competed with colonial foodstuffs, ores, and petroleum for space on the endangered merchant vessels. This grim fact imperiled everything in the European war strategy. It threatened the British war effort; if things got worse, it threatened mass malnutrition for the islanders. The heavy losses suffered by oil tankers meant that only two to three months of fuel remained in Britain’s storage tanks, but how could the country fight, or live, without fuel? This crisis also threatened the Arctic convoys to aid Russia, and the Mediterranean convoys to aid Malta and Egypt. It threatened, by extension, the entire Egyptian campaign, for Britain could scarcely send military reinforcements via Sierra Leone and the Cape of Good Hope to Suez if its own lifelines were being crushed. It even threatened unrest in parts of East Africa and India that had come to rely upon seaborne food imports. And it absolutely threatened the assumptions behind Operation Bolero (later renamed Overlord), which called for a rapid and massive buildup of the U.S. Army and the Army Air Forces in the British Isles in preparation for a second front in Europe; it would have been ironic to have sent 2,000 American heavy bombers and millions of GIs to England only to find that they had no fuel. Churchill later stated in his memoirs that, of all struggles of the war, it was the Battle of the Atlantic that he most worried about; if it was lost, so too might be Britain’s gamble to fight on in 1940.
In addition, although the Admiralty did not possess an exact tally of the enemy’s U-boats, there did seem to be an awful lot more of them. In the course of 1942 Allied warships and aircraft had destroyed eighty-seven German and twenty-two Italian submarines. But the Third Reich was also gearing up its war production and had added seventeen new U-boats each month during that year. By the end of 1942, therefore, Doenitz commanded a total of 212 submarines that were operational (out of a grand total of 393, for many were working up, training new crews, or receiving new equipment), very significantly more than the 91 operational craft he had had (out of 249) at the beginning of that year.2 Although victory in the Second World War was critically affected by each side’s inventiveness, technology, and organization, not just by sheer numbers, the blunt fact was that numbers did count. And by the time of the Casablanca conference it seemed that the Germans were having greater success at sinking Allied merchantmen than the Anglo-American forces were in sinking U-boats. Worse still, more and more U-boats were entering the fray.
In the months that followed, therefore, the prime minister’s nightmare appeared to be coming true. As March and April 1943 arrived and the convoy traffic to the British Isles resumed at a higher rate, so too did merchant ship losses. February’s total doubled that of the previous month, and in March the Allies lost 108 ships totaling 627,000 tons, making it the third-worst month on record during the war. What was more, nearly two-thirds of those ships were sunk in convoy; one was no longer talking here of the happy U-boat pickings of individual merchant ships off the well-lit shores of America early in 1942, or of the almost equally easy raids upon Allied shipping routes in the South Atlantic. What was also truly alarming was that the losses had occurred chiefly along the single most important convoy route of all, that between New York and Halifax and the receiving ports of Glasgow and Liverpool. Between March 16 and 20 the greatest encounter in the entire Battle of the Atlantic saw Doenitz throw no fewer than forty U-boats against the two eastbound convoys HX 229 and SC 122. This epic fight will be analyzed in more detail below, but the result was awful for the Allies: twenty-one merchant ships totaling 141,000 tons were sunk, with the loss of only one U-boat. In the Admiralty’s own later account, “The Germans never came so near to disrupting communications between the New World and the Old as in the first twenty days of March, 1943.”3 These ever-rising losses suggested, among other things, that the whole principle of convoy as the best means of defending maritime commerce was now in doubt.
The Strategic and Operational Context
The British Admiralty’s problems were nothing new in the annals of naval warfare. The protection of ships carrying goods at sea from hostile attack is one of the oldest problems in the history of war and peace. Even at the height of the Roman Empire merchants and consuls in Sicily and North Africa complained about the depredations of pirates against the grain, wine, and olive oil trades. Fifteen hundred years later Spanish commanders fumed at the plundering by Dutch and English raiders of their galleons bearing silver and precious spices; only a generation or two afterward the Dutch found their long-haul trade with the East Indies under French and English assault at sea. The age of European expansion and then of the Commercial Revolution (sixteenth to eighteenth centuries) had moved ever greater shares of national wealth onto precarious maritime routes. In the age of Charlemagne, the dependence of rulers and peoples upon command of the sea was negligible. By the time of, say, the Seven Years’ War (1756–63) it was critical in both the Atlantic and Indian Oceans, at least for all advanced economies. If a west European nation lost control of the trade routes, it was most likely also going to lose—or at least not win—the war itself. This was the message of that classic work, The Influence of Sea Power upon History (1890), composed by the American naval author Alfred Thayer Mahan.
Mahan’s ideas influenced the admiralties of Britain, Germany, Japan, the United States, and many lesser navies. The key belief was that the only way to gain command of the sea was to have the most powerful battle fleet afloat, one that would crush all rivals. Lesser forms of naval warfare, such as commerce raiding and cruiser and torpedo-boat operations—la guerre de course—didn’t count for much, because they didn’t win wars. It was true that during the Napoleonic Wars French predators had seized many independently sailing British merchantmen, but once the latter were organized in convoys and given an escort of warships, the sea routes were secure behind Nelson’s assembled fleets. The same truth revealed itself, albeit at great cost, during the First World War. For three years, and even though the Grand Fleet had command of the sea, Allied merchant ships steaming on their own were picked off in increasing numbers by German U-boats. After the Admiralty was compelled by the British cabinet to return to the convoy system in 1917, losses to enemy submarines dropped dramatically. Within a short while, moreover, the Allied warships would possess asdic (sonar), so for the first time ever they could detect a solid object under water. Provided one had command of the sea on the surface, it was argued, one would also control the waters below. A submarine would thus be as recognizable as the sails of a French frigate 150 years earlier. Such was the prevailing assumption of naval staffs in the years following the Treaty of Versailles, 1919. Convoys, plus sonar, worked.4
Before we examine how and why that assumption was challenged by the renewed German U-boat threat during the first half of the Second World War, a couple of very important, though clashing, strategic-operational assumptions also need to be considered. The first of these, rarely articulated, is that one really didn’t need to sink surface commerce raiders or submarines to win the maritime war. So long as the Royal Navy shepherded without loss a group of fifty merchantmen from, say, Halifax to Liverpool, it had won. The larger Allied strategy was to keep Britain in the fight and then to make it the springboard for an enormous invasion of western Europe. Thus, if every transatlantic (and South American, Sierra Leonean, and South African) convoy got to port safely without ever encountering U-boats, the war was being won, ship by ship, cargo by cargo. Even if the convoy escorts had to face a serious submarine attack but could beat off the predators, all would still be well. The task of the shepherd was to safeguard the sheep, not to kill the wolves.
The opposite argument was that killing the wolves had to be the essence of Allied maritime strategy. It too had its own logic: if the threat to the sea-lanes was forcibly removed, all would be fine and one of the Casablanca war aims could at last be implemented. In today’s language, the prevailing authorities cannot wait for terrorists to attack the international system but have to go and root out the terrorists. In maritime terms, therefore, a navy charged with protecting its merchant ships would either go on a submarine hunt or, an even bolder tactic, simply drive its convoys through U-boat-infested waters and force the submarines to fight—and be killed.
The first of these two convoy strategies was clearly defensive; the second (whether submarine hunting or forcing the convoys through) was equally clearly offensive. Both visions, it is worth noting, involved a tricky, interdependent three-way relationship between the merchant ships, the U-boats, and the naval and aerial escorts, not unlike the children’s rock-paper-scissors game. If the convoys could avoid an encounter or have the U-boats beaten off, fine for them; if the U-boats could get at the convoys without destruction from the escorts, fine for them; and if the escorts could destroy enough submarines, fine for them.
In the harsh world of the North Atlantic between 1939 and 1943, however, neither an Allied defensive operational strategy nor an offensive one was possible on its own. The way forward had to be achieved by a combination of both options, depending on the ups and downs of what turned out to be the longest campaign of the entire Second World War. And this route was, geopolitically, the most important maritime journey in the world. Of course the other Allied trade routes mattered, and all faced the same operational and logistical difficulties, or sometimes (as with the Arctic convoys) even greater ones. But maritime security across the Atlantic was the foundation stone of all Anglo-American grand strategy in the European theater. With a look forward to the remaining chapters of this book, it is worth restating the many interconnections. Winning this Atlantic battle preserved Britain’s own very large military-industrial base. Britain was also the unsinkable aircraft carrier for the Allied strategic bombing campaigns, and the springboard for the eventual invasion of western Europe. Britain was the port of departure for most of the convoys to northern Russia and to the Mediterranean; it was the source for the many troopship convoys that Churchill dispatched, via the Cape, to Montgomery in Egypt and the Middle East. Controlling the Atlantic was the sheet anchor of the West’s plans to defeat Italy and Germany.
The top-to-bottom logic chain of Allied grand strategy here is also unusually clear, a fine example of Millett and Murray’s concept of the multilevel nature of “military effectiveness.”5 The political aim was the unconditional defeat of the enemy, and the return to a world of peace and order. The strategy to achieve that purpose was to take the war to the enemy by all the means that were available: aerial, land-based, naval, economic, and diplomatic. This required decisive successes at the operational level, and in all the areas covered in the chapters of the present book. It would be foolish to argue about which of those operational regions was more important than others (even if the Combined Chiefs of Staff had to do so as they wrangled over allocating resources); they all were part of Allied grand strategy. What is incontestable, however, is that if the British, the Americans, and their smaller allies were to reconquer Europe from fascism, they first of all had to have command of the Atlantic waters.
Yet control of that vital route was itself determined, in the last resort, by a number of key technical and tactical factors. In other words, there is also in this story a clear example of a bottom-to-top logic chain. Every individual merchant ship that was preserved and every individual U-boat that was sunk by Allied escorts directly contributed to the relative success rate of each convoy. The tactical success rates of each single convoy contributed to the all-important monthly tonnage totals, and those monthly tonnage totals were the barometer to the winning or losing of the Battle of the Atlantic. That operational battle, as we have argued, was key to victory in western Europe and the Mediterranean. And winning in the West was a part of the strategic tripos—victory in the West, victory in the East (Eastern Front), and victory in the Pacific/Far East.
The Battle of the Atlantic was an operational and tactical contest that hung upon many factors. The first of these, from which all the others flowed, was the possession of efficient and authoritative organization. This was so basic a point that it is often taken for granted, yet on brief reflection it is clear how important were the structures of command, the lines of information, and the integration of war-fighting systems. Both sides benefited greatly, of course, from the experiences of the epic campaign in the Atlantic during the First World War, and by the post-1919 lessons drawn from them. In terms of simplicity of command, Doenitz had it easier, for the U-boat service was separate from the German surface navy, and it became easier still for him when the failure of a squadron of heavy ships to destroy an Arctic convoy in the last days of 1942 led to an explosion of rage on Hitler’s part and to Grand Admiral Erich Raeder being replaced as commander in chief of the entire navy by Doenitz himself at the end of January 1943. Doenitz decided to remain commander of U-boats, so as to keep control of submarine operations, and it is evident that he found it much easier to obtain the Fuehrer’s backing than his predecessor had. This did not mean that he had no organizational fights. There was a constant struggle to gain the necessary share of war materials (steel, ball bearings, electrical parts, antiaircraft weaponry) against the enormous demands of the Wehrmacht and the Luftwaffe. And, as we shall see, Doenitz had the greatest difficulty in getting aerial support for his boats. Nonetheless, it was an enormous advantage to have a single and very experienced authority directing the entire U-boat campaign.