Intelligence in War: The Value--And Limitations--Of What the Military Can Learn About the Enemy (35 page)

Nevertheless, Midway demonstrates that even possession of the best intelligence does not guarantee victory. Nimitz, Spruance and Fletcher had the enemy’s plans, thanks to the relentless intellectual effort of Rochefort and his fellow cryptanalysts, laid clear before them, or as clear as the obscurities of war will ever allow. They had, all the same, nearly lost. A little less intuition by McClusky of Bombing 6, a little more intellectual resolution by Admiral Nagumo and it would have been the carriers of TF 16 and 17, not those of Yamamoto’s Mobile Force, which would have been left burning and bereft in the bright waters of the Pacific on 4 June 1942. Japan would still have lost the Pacific War; but how much longer would it have taken the United States to triumph?

CHAPTER SEVEN

Intelligence, One Factor Among Many:
The Battle of the Atlantic

T
HE OFFICIAL HISTORIAN
of British intelligence in the Second World War, Professor Sir Harry Hinsley, made muted claims for its importance. It did not, he stated firmly, win the war; but it did shorten it.
¹
It did so particularly, he argued, by the part it played in the successful conduct of the Battle of the Atlantic, first by preventing the domination of the U-boats in the last six months of 1941, and again in the winter of 1942–43, and finally by contributing heavily “to the defeat of the U-boats in the Atlantic in April and May 1943 and then to the Allied success in so crippling the U-boat command during the second half of 1943 that it could never return to the convoy routes.”
²
These achievements, though put strictly by Professor Hinsley into the context of a far wider and more complex war, are impressive, for it was upon the ability of Britain to survive U-boat attack on its oceanic supply routes that its capacity to wage war depended; and, had Britain not sustained the effort in the seventeen months between the fall of France in June 1940 and Japan’s attack on Pearl Harbor in December 1941, Hitler would have completed his conquest of Western Europe, perhaps defeated the Soviet Union and then been able to deny the United States entry to the continent.

Defeat in the Battle of the Atlantic would have been a catastrophe. No one recognised that more clearly than Winston Churchill, who wrote, in his magisterial history of the Second World War, that “the only thing that really frightened me during the war was the U-boat peril . . . How much would the U-boat warfare reduce our imports and shipping? Would it ever reach the point where our life would be destroyed? Here was no field for gestures or sensations; only the slow, cold drawing of lines on charts, which showed potential strangulation.”
³

Strangulation would have been slow; but had Admiral Dönitz, Hitler’s U-boat chief, been given the time, it would have been sure. Dönitz was a U-boat officer of the First World War who, in the inter-war years, when Germany was denied possession of a submarine fleet, had worked out in cold theory how to conduct a campaign of commerce destruction that would destroy an enemy’s—meaning Britain’s—merchant navy. Dönitz’s tool of experimentation was the surface torpedo boat, which the Versailles Treaty allowed Germany to possess. Well before 1936, when Hitler succeeded in extracting from Britain agreement to his rebuilding of a U-boat force, Dönitz had, by trials at sea, designed a scheme of torpedo-boat attack which was to underlie the “wolf pack” tactics of the Battle of the Atlantic. Whether the target was a convoy of merchant ships or a squadron of warships (“itself a convoy”) the technique must be to make contact by daylight, with a dispersed patrol line, hang on at the limit of visibility and then, under cover of darkness, deliver the torpedo attack. The surfaced U-boat, Dönitz argued, was a torpedo boat, and the capabilities of the one predicated those of the other.
⁴

At the outbreak of the Second World War, Germany once again had a U-boat fleet; but it was small, only fifty-six boats, thirty of which were tiny coastal models. The principal ocean-going submarine was the Type VII, of which there were eighteen in service, 220 feet long, capable of 17 knots on the surface under diesel power, 7H knots submerged on its electric motors. It mounted a 3.5-inch gun and had four bow and one stern torpedo tube, for which there were nine spare torpedoes. The crew numbered forty-four. During 1939 the larger Type IX was introduced but, though it mounted a heavier gun, had six torpedo tubes and sixteen spare torpedoes and a operational range of 11,500 instead of 8,500 miles, it was reckoned by Dönitz less suitable than the Type VII for convoy battles, being slower to dive and less manoeuvrable. In 1939 there were eight Type IX.
⁵

U-boats, in the early days of the war, found their targets by patrolling the regular shipping lanes leading to the United Kingdom, which they reached by going round the north of Scotland; the English Channel was closed from the outset. Boats patrolled independently, scanning the sea by periscope during the day, surfacing at night. To begin with, there was little co-operation between the few boats on station—usually fewer than fifteen—and Dönitz made little attempt to co-ordinate their operations.

The U-boat commanders’ target was the British merchant fleet, still the largest in the world by far, with 3,000 ocean-going ships and a carrying capacity of seventeen million tons. It was fully employed, since Britain was dependent on imports for over a third of its food and most of its raw materials, except coal. Annual imports in 1939 totalled fifty-five million tons, to be paid for largely by the export of finished or semi-finished manufactures. Britain, uniquely among the major powers, was a country reliant upon maritime trade, both inward and outward. Interruption to sailings quickly produced shortages, as well as harm to credit. Sinkings threatened permanent damage, since the output of all shipyards in Britain and the empire amounted to only a million tons a year, or about 200 merchantmen or tankers of average size.

Dönitz, a keen student of the economics of maritime trade, was well aware of Britain’s vulnerability and, as a result of his experience in the First World War, believed firmly, indeed with passionate conviction, that an expanded U-boat arm, attacking without the restrictions imposed by traditional prize regulations, could end Britain’s ability to wage war. Between 1914 and 1918, the German navy sank 4,837 Allied merchant ships, totalling over eleven million tons, most of them British, most sunk by U-boats and most in the period from 1917 onwards. Germany had launched 365 U-boats and lost 178.

On 28 August 1939, as Hitler completed his preparations to attack Poland, Dönitz submitted to Admiral Raeder, the head of the German navy, his proposal for a major expansion of the U-boat fleet. He wanted 300 U-boats, together with some larger submarines to serve as supply ships to the attack boats, which would allow fifty U-boats to be kept on patrol on the shipping routes at any one time; he had elsewhere calculated that if each sank three ships a month, a rate achieved in the Great War, half the British merchant fleet would go down in a year, at a rate vastly outstripping replacement. Britain would starve, as it had nearly done at the end of 1917, and be forced to surrender. He also wanted the U-boat building programme to be placed under the control of a single officer and, at a conference held on 9 September, six days after the war with Britain had begun, proposed himself for the post. “This task now becomes the most important of all, which should be under the direction of an officer with expert knowledge of the theory and practice of U-boat warfare.”
⁶

Raeder demurred. He recognised Dönitz’s talents and dedication but wanted him to remain in day-to-day command of the existing U-boat fleet, though he gave assurance that it would be greatly and rapidly expanded. Raeder was probably right to decide as he did. Dönitz, though physically unprepossessing, humourless and intellectually obsessive, had undoubted qualities of leadership. His U-boat men, who included at the outset some buccaneering captains of exceptional seamanly quality, always looked up to him, craved his approval and served devotedly to the end. Theirs was a horrible life. The U-boat was cramped and smelly, always either too cold or too hot and usually dripping with damp. Food soon went off, clothes were clammy, toilet arrangements foul and the air for much of the time scarcely breathable. U-boat life was characterised by prolonged periods of boredom, particularly as the war drew on and crews had to spend long periods submerged motoring to their patrol stations. Above all, it was extremely dangerous. Of the 40,000 sailors conscripted into the U-boat arm—unlike the submarine services of the U.S. or Royal Navies it was not voluntary—28,000 were killed in action, most of them drowned as the result of attack by escort vessels of the Royal Navy, Royal Canadian Navy and United States Navy or their associated air forces and naval air arms.

ANTI-SUBMARINE WARFARE

During the First World War, 178 of the 365 German U-boats built by Germany had been lost at sea, despite the then Allied lack of any effective means of detecting submerged boats. Acoustic methods were employed, and aircraft and airships attempted to spot U-boats from the air in shallow waters, almost always unsuccessfully. Most U-boats sunk, at least forty-eight, fell prey to mines in mine barriers. Ramming, by warships or merchantmen, accounted for another nineteen, attack by British submarines seventeen. Destruction by depth-charge, the specific anti-submarine weapon, was responsible for only thirty losses.
⁷

The depth-charge was a bomb containing usually 40 pounds of high explosive, dropped from a rack over the stern or projected abeam, and activated by a pressure fuse, which could be set to explode at a chosen depth. It created high-pressure waves and, if detonated close enough to a U-boat hull, cracked its plates. Accurate depth-charging was fatal but accuracy was difficult to achieve; throughout the Battle of the Atlantic, but particularly in the early days, damage rather than destruction was a common outcome of depth-charging. After 1942, depth-charging was supplemented by the firing of large numbers of contact bombs, from the Hedgehog and subsequent Squid systems, which, given accurate location, could be deadly. In mid-1943 another weapon appeared, the Mark 24 Mine so-called; in fact, an acoustic torpedo, dropped from an aircraft to home on U-boat propeller sounds. Lethal in most circumstances, it suffered from the disadvantage of being deemed so secret that it could be launched only under special conditions. Aircraft also dropped depth-charges and fired high-explosive rockets against surfaced or submerging U-boats, those motoring to Atlantic patrol lines across the Bay of Biscay providing most of the targets.
⁸

Most of these developments lay far in the future at the outset of the U-boat war, when the advantage lay heavily with the Germans. The advantage would have been decisive, had Dönitz been able to deploy the numbers he desired and would eventually achieve. Even so, the advantage was enhanced by the enemy’s lack of anti-submarine warships. Britain in 1939 appeared to have a sufficiency of escorts. The Royal Navy deployed 128 destroyers and 35 sloops.
⁹
Most of the destroyers, however, including the superb Tribal and Javelin classes, were high-speed ships, designed to accompany the battle fleet and lacking the endurance to linger as convoy escorts. Many of the older destroyers had been built during or soon after the Great War and were coming to the end of their lives. The Hunt-class destroyers, designed specifically as escorts, were entering service but were too few in number as yet—only twenty—to tip the balance. The sloops were generally too old to be effective. A whole new generation of escorts—slow but sturdy corvettes, modelled on South Atlantic whalers, and speedier frigates—were in gestation but had not yet reached the fleet. Trawlers and drifters from the fishing fleet had been pressed into service; but they were too small and too slow to make capable escorts. The result was that convoys had too few escorts to be able, when attacked, to defend themselves.

Convoy was adopted by the Admiralty at the outset of the war, in sharp contrast to its policy during the First World War. Then the admirals had resisted it, for wholly mistaken reasons. Convoy was a hallowed British maritime practice, which had protected British trade from attack by the French fleet and roving corsairs throughout the wars of the French Revolution and empire. At the outbreak of the Great War, however, and until late in 1917, the Admiralty had mistakenly calculated that, given the submarine’s ability to mount attacks submerged, the practice of massing merchantmen in convoy merely multiplied the targets available to a predator, which the navy lacked the means to locate. It was therefore better, it was concluded, to let ships sail independently, thereby, apparently, forcing submarines to choose their targets singly and, so it was supposed, with greater difficulty. The Anti-Submarine Division of the Admiralty also shrank from the task of providing escorts for what it believed were 5,000 sailings into and out of British ports each week.