Why the Allies Won

by Richard Overy

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  The desperate efforts to stem the tide in the Pacific had immediate repercussions for the war against Germany and Italy. Although the American service chiefs wanted to send an army into Europe as soon as possible in order to get to grips with the enemy they regarded as the more dangerous, they were compelled to accept that not everything could be done at once. There were shortages of ships, trained men and equipment of every kind. So generously provisioned was each American division with food, vehicles and services that it required 144,000 tons of shipping space to move just one infantry division, and almost a quarter of a million tons for one that was armoured.45 By October 1942 only one and a half American divisions had reached Britain. With great reluctance Admiral King, and his army colleague General George Marshall, had to accept that no invasion of continental Europe was possible in 1942, though they pressed all year for a firm commitment that some kind of amphibious assault would take place in 1943 against German-held territory.46

  The British had recognised sooner than their new ally that it was foolhardy to attempt an assault on Europe without adequate numbers and prolonged preparation. Their preference was for limited seaborne operations in the Mediterranean theatre, where British Commonwealth troops were already engaged in a holding operation to prevent Italian and German forces from reaching the Suez Canal and the oilfields of the Middle East. American leaders found British preoccupation with the Mediterranean hard to understand. American military doctrine was straightforward: take the offensive with all available force against the main force of your adversary. British strategy was less direct, more subtle, honed by years of experience in fighting larger powers with small resources. British leaders knew that they faced disaster if they pitted an inadequate land army against Germany in 1942; they had been defeated in just such an attempt two years before, with the whole French army at their side. Naval power allowed them the luxury of picking easier fields of combat, against the weak links in the enemy’s armour. There was nothing particularly special about the Mediterranean. Britain had no large settler community there; from Gibraltar to Aden she had only a few thousand colonial officials and traders. There were no vital economic interests at stake. Although she hoped to deny Middle Eastern oil to the Axis powers, almost all the oil used in Britain came from the New World by 1942.47 The chief argument for Allied presence in the Mediterranean was that here they were fighting a corner of the war that they could win in 1942, against weak Italian forces spiced up with a handful of German divisions and air squadrons.

  It was not a glamorous alternative, but it was a realistic one. Against the strong advice of his military chiefs Roosevelt agreed in July 1942 to a diversion of scarce shipping and equipment to supply an invasion of North Africa, codenamed ‘Torch’. Churchill hoped that the decision would lead to great things: the defeat of Italy, the reopening of the Mediterranean to Allied sea traffic, and the cutting of a route into the ‘soft underbelly’ of Axis Europe, through the Balkan peninsula, or Yugoslavia or southern France. For the Americans it was the least they would consider doing. They refused to regard Torch as an alternative to the invasion of northern Europe, and accepted it only on the understanding that the larger enterprise would not be long postponed.48

  The joker in the pack was the German submarine, or U-boat (‘U’ being short for Untersee). No Allied strategy was possible across the Atlantic Ocean without the defeat of the submarine. The supply of goods and oil to Britain and the Soviet Union was threatened on every route, from the Arctic convoys to Murmansk and Archangel, to the long hauls from Trinidad or around the Cape of Good Hope. Any operation, whether in the Libyan desert, in north-west Africa, or across the Channel, relied on securing the sea-lanes first. Almost immediately on American entry into the war the advantage in the Battle of the Atlantic swung towards the submarines, and Allied naval power faced its most severe test.

  After the successes of 1941 the German navy was no longer the Cinderella of the German armed services. From only a handful of U-boats in 1939, the submarine arm was now being supplied with thirty new boats a month; it had almost three hundred in total at the beginning of 1942 and almost four hundred by the end. The German Commander-in-Chief, Grossadmiral Erich Raeder, now saw the submarine as the key to ‘decisive victory’. Even Hitler, whose grasp of naval affairs was rudimentary, came round to the view in April 1942 that ‘victory depends on destroying the greatest amount of Allied tonnage’. By June he was completely converted: ‘the submarine will in the end decide the outcome of the war.’49 The strategy was unsophisticated. U-boats were ordered to sink Allied shipping when and where they could, merchant ships for preference, naval vessels if they found themselves under attack. The commander of submarines, Admiral Karl Dönitz, estimated that a monthly sinking of 700,000 tons would be more than enough to erode combined Anglo-American shipping capacity and slow down or even stop Allied operations. The aim was to maintain sinkings at at least 4-500,000 tons a month, the level achieved in December 1941. The submarine war was a war of closely calculated attrition, its success measured not in any one engagement but in the calendar of stricken tonnage.50

  Dönitz shared his chief’s conviction that the Anglo-Saxon powers would be defeated ‘only at sea’.51 The son of a Berlin engineer, Dönitz joined the navy straight from school in 1910, and rose during the Great War to command a submarine until captured by the Royal Navy shortly before the war’s end. He was regarded by all his superiors as an outstanding officer, dedicated, cool-headed and sociable. He bitterly resented Germany’s defeat and welcomed the revival of German strength under Hitler. In 1936 he was appointed Führer of the German U-boat arm and dedicated himself singlemindedly to the task of building up a sufficient force of submarines to alter German prospects decisively in a renewed naval war with Britain.52

  He always regarded three hundred as the optimum number of submarines to make Britain’s sea-lanes unnavigable, and by 1942 he had all but achieved this figure. This did not mean there were three hundred submarines in action at any one time, for large fractions were always in transit, refitting or training; but it did mean eighty or ninety were operational at any one time, most of them in the Atlantic. The bulk of the boats were the Type VII, weighing approximately 750 tons, with a maximum speed of 17 knots, a radius of 8,000 miles and an armament of eleven torpedoes. In 1942 they were supplemented by the Type IX boat, of 1,100 tons with a cruising range of 13,450 miles and 22 torpedoes.53 The boats were organised in groups of three, and were formed into the wolf-packs only when a definite convoy sighting had been made. A control room in France tracked the progress of both U-boats and merchant ships, directing the boats to the contact point by brief radio messages. Some U-boats were sent to the coast of Africa or to the Indian Ocean, returning after eighteen-month voyages with crews parched by the sun and bearded almost beyond recognition. But Dönitz preferred the principle of concentration of force against the richest pickings on the Atlantic trade lanes. Submarines followed the ships.

  In the early months of 1942 there was no doubt about the target. With American entry into the war the submarines were sent to the far side of the Atlantic to attack the concentration of shipping on America’s vulnerable eastern seaboard. The submarine packs were given suitably predatory names – Leopard, Panther, Puma etc – and ordered to begin Operation ‘Paukenschlag’ (‘Drumbeat’). For the submariners it was the start of ‘fortunate times’ once again. So easy was the hunting that the submarines operated on their own rather than in groups. From the middle of January they began to reap a remarkable harvest. The Americans sent merchant ships and oil tankers without escort, unconvoyed, using radio so openly that the submarines had no difficulty in closing on the isolated vessels as they each betrayed their position. When the submarines surfaced near the coast they met an extraordinary sight. The seaboard cities were a blaze of light, illuminating the silhouettes of slow-moving ships passing along the familiar peacetime routes, their own lights still shining. The submarines fired at will. In four months 1.2 mil
lion tons of shipping was sunk off the American coast alone. The Allies lost 2.6 million tons of shipping between January and April, more than had been lost in the Atlantic in the whole of 1941. U-boat losses in January were only three, in February only two.54

  This situation could not last. The American navy had encouraged cargo ships to sail independently, without escorts, because of what it had seen of damage to the convoys in 1941, when British and Canadian escort vessels had been unable to cope with the submarine once it had sighted its prey. The navy’s offensive traditions inclined it to try to hunt down the submarines using specialised naval groups along the coast, but the patrols were ineffectual, looking for a needle in a haystack. Not surprisingly, few contacts were made, while the wolf-packs gobbled up the defenceless merchantmen. Only a shortage of submarines prevented an even worse disaster, for at just the point that Dönitz hoped to tighten the screw Hitler ordered U-boats to Norway to prevent what proved to be a phantom invasion. By the time the submarines were available in strength there had occurred a revolution in American tactics. Convoying was instituted, together with a blackout and radio silence. Continuous air patrols forced the submarines away from the coast, down to the Caribbean and farther out into the Atlantic.

  Here there were still plenty of opportunities. During 1942 the submarine force had the benefit of a vital edge in the intelligence war. The German naval intelligence service, the B-Dienst, successfully broke the British Naval Cypher No. 2 in September 1941, and three months later was able to read the new Cypher No. 3, which was used by the British, Americans and Canadians for controlling the movement of all trans-Atlantic convoys. In February 1942 the Allies lost their newfound ability to read the German Enigma traffic – machine-enciphered signals thought by the Germans to be impenetrable (known on the Allied side as Ultra) – when the naval Triton cipher was altered. This intelligence black-out lasted until the end of the year. It was now possible for German submarines to be directed accurately into the path of oncoming convoys, but extremely difficult for the Allied navies to know exactly where the wolf-packs lay in wait.55 Other advantages piled up. New supply submarines of 2,000 tons – nicknamed ‘milch-cows’ – were sent out to enable the smaller boats to refuel and rearm without having to make the long trip back to the submarine bases in Europe, during which time they were completely ineffective. The radio messages which held the wolf-pack together and directed it to the target were converted to a concentrated form to make their duration as brief as possible, in order to avoid detection.

  Yet for all the tactical sophistication the submarines remained vulnerable to the well-managed, heavily-escorted convoy, or to air patrol by converted bombers and flying boats, armed for anti-submarine warfare. During 1942 the radius of air action was extended, with great arcs of the Atlantic becoming accessible from Ireland, Iceland and Newfoundland. What was left was an area 600 miles wide in the mid-Atlantic, the so-called ‘Atlantic Gap’ or ‘Black Pit’. The gap stretched from Greenland in the north through to the area around the Azores, and it was here that Dönitz concentrated his submarines from the middle of the year. The wolf-packs lived in the gap, attacking convoys as they left air cover and breaking off the attack when they regained it. The packs would then refuel from the milch-cows and await the next convoy. The attacks carried great risks, but the rewards were substantial. In 1942 sinkings in the Atlantic reached 5.4 million tons; total Allied losses reached 7.8 million tons, 1,662 ships in all. This was a rate of loss difficult to sustain. British imports sank to one-third of their peacetime level; by January 1943 the British navy had only two months’ supply of oil left. ‘The only thing that ever really frightened me during the war’, Churchill later wrote, ‘was the U-boat peril.’56

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  In an area as vast as the Atlantic the submarine was an inherently difficult enemy to defeat. Cruising on the surface it could outrun most ships; submerged it was invisible without the right scientific equipment. The initiative lay with the submarines who could choose where and when to engage enemy traffic. The Allies by 1942 were faced with a daunting but not insoluble mission. They adopted two very distinct approaches. The first was to find ways of avoiding the submarine altogether. Indeed the chief priority was not to sail pell-mell into a submarine trap in the hope that a handful of small escort vessels could sink the attacker in time, but to get across the Atlantic entirely unmolested. If this was galling to naval commanders who relished combat, it was none the less the best way of getting supplies (and thankful sailors!) across the ocean. The second was to find a way of accurately locating submarines so that effective anti-submarine forces, naval and air, could be brought to bear without wasting endless time on long sweeping searches. It was never enough simply to avoid the submarines: at some point they had to be fought.

  The common denominator required for both strategies was precise knowledge of the movement of submarines. Convoys could then take evasive action; aircraft and combat vessels could close in on the betrayed location. Accurate intelligence about the whereabouts of U-boats was the first building block in the Atlantic Battle, but it was frustratingly difficult to secure. For much of 1942, with Allied cryptanalysis blinded by Triton, the navy relied on the Submarine Tracking Room set up in the Admiralty at the outbreak of war. The Tracking Room used a wide variety of intelligence sources, from agents’ reports in the submarine bases on the French coast, to bearings reported by the units for radio interception scattered around the Atlantic rim. It was deliberately housed next to the Trade Plot Room, from which the global movement of merchant vessels was controlled. Intelligence from the Tracking Room was immediately available to alter the movements of merchant shipping. The room was run not by desk-bound sailors but by civilians – academics, economists, lawyers – drafted in to bring intelligence, in its conventional sense, to bear on the sea war. In charge was Rodger Winn, a barrister of exceptional talent, who devoted himself, to the point of physical collapse, to providing the best estimate day by day of the number and position of submarines in the Atlantic. Even without cryptographic intelligence the Tracking Room was able to warn the American navy of the impending assault on east coast shipping lanes in January. It did not take Admiral King long to realise the value of accurate plotting, and a similar room was set up in Washington, which cooperated closely with its British counterpart for the rest of the war.57 The intelligence effort paid rich dividends. Between May 1942 and May 1943 105 out of 174 convoys sailed across the Atlantic without interference from submarines; out of the 69 sighted by the wolf-packs 23 escaped without attack and 30 suffered only minor losses. Only the remaining 10 per cent were severely depleted.58

  Good intelligence was the first step. It was up to the convoy commander and his naval escort to do the rest. However, there were obvious weaknesses in the escort system. Escort vessels were in short supply, even more so when the crisis in the Pacific drew American vessels away from the Atlantic. Many of the escorts were obsolescent boats, converted to a role for which they were inadequately prepared and armed. The task of the escort commander was hazardous and demanding. In all weathers, with only imprecise knowledge of the exact whereabouts of the submarine packs, he had to remain constantly vigilant, shepherding his loosely-formed flock of merchantmen scattered over miles of ocean, and rescuing stragglers. Air cover was almost non-existent. The large aircraft carriers were needed elsewhere, and the conversion of tankers and cargo vessels to a carrier role was a slow process, their potential realised only late in the day. Until 1942 the training for escort duty was rudimentary. Commanders were expected to devise their tactics on the ocean. When confronted with a U-boat some commanders ordered the escorts to give chase, leaving the merchantmen weakly defended. Others concentrated on herding their vessels out of danger, using the escorts like so many sheepdogs, snapping at the heels of slower transports to save them from the wolves. But gradually a common set of tactics emerged: when numbers permitted, the escorting ships would divide into two groups, the larger part protecting the cargo vessels, a small
er group hunting the convoy perimeter for submarines.

  Direct attack on the submarines required information of a different kind. There was little chance of a kill without some way of locating to within feet the position of the enemy. At night-time, against submarines operating on the surface, this knowledge could not be acquired with conventional technology and naval tactics, and chance played a part in any densely packed convoy battle. During 1941 and for much of 1942 the number of submarines destroyed in all theatres remained small, only 35 in 1941, and only 21 in the first six months of the following year. This was a rate of attrition that could comfortably be supported by the U-boat arm. The only way to increase that rate was to apply to the naval conflict the new weapons of war – long-range aircraft, radio and radar.

  The importance of aircraft was plain to see. Wherever air patrols were in operation submarine activity was much reduced. Aircraft were ‘the great menace for the submarines’ Dönitz told Hitler in September 1942. But until well into 1942 the aircraft was a limited weapon in the actual destruction of U-boats. The number of aircraft allocated to over-sea duty was small in relation to the task, and it proved difficult to persuade the RAF to divert larger bombing aircraft from the attack on Europe to the war at sea. The original anti-submarine bomb proved to have almost no destructive power, and was replaced by an aerial depth-charge, though only in the course of 1942 were weapons of enhanced destructive power, charged with a new explosive (Torpex), finally introduced.59 The central problem for the anti-submarine aircraft was to find the submarine and, having found it, to sustain an attack before it submerged to the safety of waters beyond the range of depth-charges. The answer lay with Radio-Direction Finding, later known by its familiar name of radar.