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BATTLE OF THE ATLANTIC

‘The only thing that ever really frightened me during the war was the U-boat peril.’—

Winston S. Churchill in Second World War, Vol. II.

ONE OF THE MOST VITAL battles of the Second World War, and certainly the longest, was that fought at sea against the German U-boats. The island fortress of Britain had to be supplied with both food and war materials so that its survival depended upon the maintenance of supremacy at sea. The Germans realised this, and after their failure in the Battle of Britain they sought by sea and air attack to close the supply routes by which the British people could carry on the war and thus bring about their starvation and surrender.

The U-boat was by far the greatest menace. In the First World War it had brought Britain to the verge of defeat; but the lesson had been forgotten. In 1939 the Royal Navy was woefully short of escort vessels while Coastal Command^* of the Royal Air Force, whose main task was to aid the Navy, was equipped with a handful of aircraft, most of them obsolescent types whose weapons were hopelessly inadequate for dealing with the modern U-boats which the Germans were constructing. Airborne radar and the other technical aids that were later to play such an important part in the battle were still in the experimental stage. Only gradually was this state of affairs remedied, and it proved most difficult to keep pace with the expansion of the German U-boat fleet and the extension of its activities to the wider spaces of the Atlantic as well as to the many focal areas of Allied shipping. Indeed, during 1942, when over six million tons of Allied merchant shipping were lost through U-boat attacks, the situation became critical, and it was not until the end of the following year that the Allies could be said to have taken the measure of the U-boat threat.

A deciding factor in this favourable turn of events was the success achieved by aircraft over the Bay of Biscay and the convoy routes in the North Atlantic during 1943. Of 145 U-boats sunk in these areas during that year, 94 were destroyed by attack from the air. Even so the Germans were not beaten and they later returned to the attack with new weapons and devices which were never completely countered. The battle continued to the end and ceased only when the last German U-boat at sea had been escorted to a British port, flying a black flag of surrender.

New Zealand airmen flew with the anti-submarine squadrons of Coastal Command during the war as pilots, navigators, wireless operators, and gunners, while a small number did useful work in various ground duties. Two New Zealand squadrons were formed in Coastal Command: No. 489 Squadron, which served mainly in an anti-shipping role along the Norwegian Coast and in the North Sea, and No. 490 Squadron, which did valuable work over the West African convoy routes. But the large majority of the New Zealanders in Coastal Command were scattered among page 4 Royal Air Force units and often among the crews of squadrons. In fact, as in Bomber Command, many of them flew in crews made up of men from various parts of the Commonwealth. Altogether, New Zealand airmen took part in the destruction of twenty-four German U-boats, and in seven of these cases a New Zealander was captain of the aircraft which made the attack. But it is outside the scope of this account to describe all their experiences during the long years of the war at sea. What is attempted in the following pages is a few glimpses of various phases of their work during the period from November 1942 to November 1943 when the Battle of the Atlantic was at its height and when aircraft played a decisive part in the struggle.

Aircraft, however, had not been ineffective in the war at sea before this period, even though the actual number of U-boats destroyed by them was small. Their defensive work in protecting convoys and in keeping U-boats submerged had been invaluable, so that many a ship owed its safe arrival to the vigilant watch maintained from the air. When independent offensive patrols were increased during the second half of 1941, aircraft were largely responsible for driving the German submarines from the Western Approaches to operate farther out in the Atlantic where targets were more difficult to locate. Prisoners taken towards the end of that year spoke with feeling of the air patrols which forced them continually to dive, while Grand Admiral Doenitz, Commander-in-Chief of the German Navy, complained that ‘aircraft were locating and attacking the U-boat dispositions so that their patrol areas were avoided by convoys’. One U-boat even surrendered to a Hudson aircraft after the latter's depth-charge attack. The vessel was subsequently towed to port and provided valuable information.

Nevertheless, inefficient weapons and the lack of suitable technical aids rendered the early air attacks more of a harassing nature. They inflicted a certain amount of damage and often forced U-boats to lose touch with convoys, but were only occasionally successful in completely destroying the enemy. The U-boat was an elusive and difficult target to attack from the air and its construction was so tough that the depth-charge then in use had to fall within a few feet of the hull in order to split it.

Throughout 1942 the air offensive had continued, but with the limited range of the aircraft then available the U-boats were able to play havoc with convoys in mid-Atlantic. However, by the end of the year, science and industry had begun to provide aircraft of longer range, an improved type of radar, and better weapons, such as the torpex-filled depth-charge and the Leigh Light for attacks by night. Along with these technical aids, new tactics were evolved which enabled air power to be employed with much greater effect in the following year.

During 1943, the main types of operational U-boats used by the Germans were vessels of 517 and 740 tons, carrying crews of about 45 and 55 respectively, although they were also building 1600-tonners for long cruises and for supply. These craft were specially constructed to withstand the underwater blast of depth-charges and had an extra pressure hull of high tensile steel. They had two sets of machinery: Diesel engines for propulsion on the surface and electric motors for use when submerged, the latter also serving as dynamos for re-charging batteries on the surface. Maximum speed on the surface was about seventeen knots but the normal cruising speed of eight knots gave an endurance of some 10,000 miles. When travelling submerged on both motors, top speed was about 7½ knots, but then battery endurance was only two hours. At lower speeds a U-boat could remain submerged much longer, but the air became so foul that normally the vessel page 5 would not stay down for more than twenty hours at a time. Towards the end of the war this handicap was overcome by fitting U-boats with the Schnorkel device—air intake and exhaust tubes that could be raised at perscope depth, enabling the air to be changed and the batteries recharged whilst the vessel remained submerged.

When on patrol the U-boat's lookout was of a high order, four men on duty at a time standing back to back in the conning tower, each searching an arc of 90 degrees. They were supplied with excellent binoculars and the watches were changed frequently. In clear weather they would often sight an aircraft at such a range that the boat could dive in time to avoid attack, but the skilful use of sun and cloud cover would defeat them. Furthermore, in a heavy sea, the watch could never be fully efficient because of the rolling of the U-boat and the spray.

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The principal weapon employed in the air attacks on U-boats during 1943 was the 250 lb. depth-charge set to explode at twenty-five feet below the surface. Aircraft carried from four to eight according to their type and the length of their patrol. They were aimed visually by the pilot but were released by an electrical distributor so that they fell in an evenly spaced stick, the idea being to straddle the U-boat so that one depth-charge fell near enough to cause lethal damage. Aircraft usually patrolled at heights up to 5000 feet according to cloud cover but the actual attack was made from about fifty feet. This had to be a short and sharp affair before the U-boat crash- dived, yet it was not easy to manoeuvre a heavy four-engined aircraft into the correct position for a successful attack while the target was still visible.