Battle of the Atlantic
In 1938 the Kriegsmarine’s Plan Z, designed by Grand Admiral Erich Raeder, Commander in Chief of the navy was set in motion. The plan aimed to give the German Navy parity with that of Britain within a decade, envisioning a surface fleet of 10 capital ships, eight aircraft carriers and almost 250 submarines. But at the advent of hostilities in September 1939 the plan failed to materialise, and Germany went to war with a greatly diminished fighting strength of just seven capital ships and 65 submarines.
During the 1930s, Britain imported over 70% of her foodstuffs, equating to 20 million tons of shipping annually. German war planners had concluded as far back as 1935 that the Atlantic sea lanes were the key to defeating the British by literally starving them into submission. Britain relied on the Atlantic lifeline not only for food but for industrial minerals, raw materials and US lend-lease tanks and equipment.
The war at sea was initiated within hours of the declaration of hostilities.
The passenger liner Athenia sailing from Liverpool to Montreal with 1,400 passengers was torpedoed and sunk by U-30 commanded by Kapitan-Leutnant
Fritz Julius Lemp. Almost 120 passengers were lost, and the head of U-boat operations Commodore Karl Donitz ordered the submarine’s log book altered to erase the event, the truth only being made known at the Nuremberg trials after the war.
In October, U-47 skippered by Gunther Prien, evaded the anti-submarine defences of the natural harbour of Scapa Flow in the Orkney Islands, north of Scotland. Firing two salvoes of torpedoes, he sent the veteran battleship HMS Royal Oak into the depths with 833 of her crew. Among those lost were Rear-Admiral Henry Blagrove,
Battle Squadron Commander, and over
100 boy seamen under the age of 18.
Prien was feted throughout Germany and decorated personally by Hitler with the Knights Cross, the first submarine officer of the war to receive Germany’s highest military honour.
Although first blood had gone to the U-boat arm, the German surface fleet had not been idle in the first weeks of the war. By 7 December the pocket battleship Graf Spee had disposed of nine merchant ships. Attracted by the maritime traffic transiting the mouth of the River Plate feeding the port cities of Buenos Aires and Montevideo, Graf Spee, headed for the south American coast.
South east of Rio de la Plata, the German vessel was intercepted by a squadron of Royal Navy ships. After a running battle, Graf Spee, severely damaged, took refuge in the Uruguayan capital Montevideo. Hemmed in by the British squadron, and unable to fight, Captain Hans Langsdorff concluded that to save the honour of the Kriegsmarine and Nazi Germany, the only remaining option was to scuttle his ship. Despite early successes, German attacks on Allied shipping failed to make a significant impact throughout 1939-40. It was the simultaneous German invasion
UK, Canada, USA
COMMANDERS
Admiral Max Horton (UK)
Admiral Royal E Ingersoll (USA)
CASUALTIES
36,200 killed (Navy) • 36,000 killed (Merchant Navy) 175 warships • 3,500 merchant ships
741 RAF Coastal Command planes
per month. Despite their devastating success, Donitz believed he could deploy his submarines more effectively and ordered implementation of the wolfpack, Donitz’s idea was to use groups of U-boats in concerted attacks on the surface at night. This would negate Allied reliance on ASDIC (the early forerunner of sonar, originally developed in 1916) leaving escort vessels blind and unable to defend their merchant charges. Deploying lines of U-boats perpendicular to the sea lanes, Donitz controlled his sub-surface wolfpacks by radio, and convoy reports were swiftly disseminated. The U-boat locating a convoy was responsible for tracking it, while transmitting a direction-finding signal on the medium band (MF/DF), enabling the remainder of the pack to home in. Radio traffic was enciphered using the sophisticated Enigma system which, while not unbreakable, was considered complex enough to resist rapid deciphering thus preventing swift counteraction. British convoy losses climbed and reached a catastrophic 1,300 ships by the end of the year.
Allied countermeasures were rudimentary at best during the early stages of the conflict. Convoy escorts were generally confined to accompanying merchant vessels in coastal areas, leaving them to cross the mid-Atlantic unguarded - the Admiralty had never conceived that ships may face more than one or two submarines simultaneously. The malaise did not last long; anti-submarine warfare training and tactical innovation was driven by newly appointed Admiral Max Horton. He emphasised ongoing training programmes, the use of technology and brilliant tactical adaptability by the likes of Captain Frederic Walker, one of the Royal Navy’s most able anti-submarine officers. Experience began to pay off. In March 1941 the Kriegsmarine was shaken by the loss of Joachim Schepke and Gunther Prien both killed while Otto Kretschmer was forced to the surface and captured.
After the German invasion of the
Soviet Union in June 1941, the lend-lease program was extended to provide aid to the Russians. Desperate to make up the massive material losses suffered by the
Red Army, Stalin demanded continuous supplies of armour and aircraft, all requiring transportation via the Barents Sea. The ships sailing on the Arctic routes to northern Russia experienced the highest losses of any convoys with one in 20 merchant vessels sunk during the perilous 2,500 miles voyage to the ports of Murmansk and Archangel. These journeys took ships within 750 miles of the North Pole where temperatures plummeted as low as -50 degrees Celsius.
In May of 1941 HMS Bulldog depth charged U-110, captained by Julius Lemp of Athenia notoriety, south of Iceland forcing her to the surface. In the process Lemp was killed and a boarding party located an Enigma machine and code books which were passed to crypto analysts at Bletchley Park. The Bulldog’s success altered the course of the struggle in the Atlantic. This Ultra intelligence as it was became known, made it possible to decode German naval signal traffic and to reroute convoys away from the wolfpacks and brought an end to the first happy time of the U-boat fleet.
Without doubt the most vital development in the struggle to dominate the Atlantic was the increasing involvement of the United States Navy during the late summer of 1941 after Churchill and Roosevelt had met in August to discuss military cooperation. Operational control of transatlantic convoys west of Iceland passed to the Americans and
simultaneously placed Canadian naval and air assets under their command even though the US was still officially neutral. The US Navy commenced convoy escort duties in September and on 11 December, just four days after the Japanese attack on Pearl Harbor, Germany declared war on the USA.
Tragically, the US Navy ignored the lessons learned by the British and Canadians and refused to adopt a coastal convoy system, sending individual vessels along regularly patrolled designated shipping routes. Towns and cities on the eastern seaboard kept their lights burning, thereby aiding U-boat navigation and illuminating ships leaving port. The consequences were disastrous. Attracted by the plentiful unescorted shipping, the Germans commenced Operation Drumbeat and between January and August 1942 instituted a second happy time, sinking over three million tons of shipping and costing thousands of lives for the loss of 22 U-boats. In May 115 ships were sunk, most of them in the Gulf of Mexico with losses rising to 122 ships in June. It was enough to convince the US Navy to accept the convoy system which, as it increased and with improved air cover, drove the U-boats to find safer hunting grounds. 1942 brought further change. Iceland was abandoned as a relay point for the convoys which were rerouted directly from Newfoundland to Northern Ireland. Admiral Donitz redeployed his U-boats back into the mid-Atlantic to concentrate attacks against these northern great circle routes and a devastating war of attrition between the Canadian Navy and the Kriegsmarine began.
In July, Convoy PQ17 lost 24 of its 35 merchant ships during a series of concentrated daylight attacks over seven days. Technologically the Germans had the advantage. U-boats were able to directionfind the Canadian units who, in turn, had not been equipped with modern radar and struggled to locate and attack the U-boats. Canadian escorted convoys made up 80% of Allied losses during this period and while their sailors fought valiantly to protect the shipping lanes, their lack of modern technology saw them brought to the brink of defeat.
Beginning in early 1943, the Kriegsmarine concentrated its U-boat fleet in the only place of relative safety that remained – the mid-Atlantic. Approximately 100 German submarines ranged the central-Atlantic gap, beyond the reach of conventional Allied airpower. The British rapidly realised that slow moving convoys to Russia, set upon by packs of up to 30 U-boats, were almost impossible to protect. In January convoy SC118 lost 11 ships with only four U-boats sunk. Further disasters followed; the attack on convoy ONS166 lasted three terrible days. The Royal Navy, aided by Canadian aircraft, fought desperately in the fog of the Grand Banks but lost 14 ships.
The frenzied struggle reached a climax mid-March when the largest wolfpack assembled during the war, totalling 40 U-boats, sank 21 ships of convoys SC122 and HX229 over the course of four days, despite determined Allied attempts to defend the merchantmen.
As events seemed at their most critical, the end of March brought a turn in the tide of battle. Very Long Range
(VLR) anti-submarine aircraft such as the B24 Liberator and the Short Sunderland became more widely available, supplemented by the long-awaited escort carriers which effectively eliminated the air gap. At this point, Allied cryptographers broke the Kriegsmarine’s operational codes which once again enabled rerouting to avoid the prowling wolfpacks. Tactics now changed; aided by Ultra intelligence, heavily guarded convoys were used as bait for the waiting German submarines which were then located and destroyed. Late in April, Convoy ONS5 consisting of 46 ships headed westward under British escort. The convoy was tracked by two converging wolfpacks and although suffering the loss of 10 ships, escort vessels sank seven U-boats. Donitz eventually ordered a withdrawal. The U-boat fleet maintained a presence in the Atlantic for the remainder of the year, but the Battle of the Atlantic was essentially over. Hounded by hunterkiller task groups with aircraft carriers and directed by Ultra intelligence, U-boat losses increased dramatically. In what became known as Black May, 43 U-boats were lost, 32 of them in the Atlantic, and Donitz conceded defeat. Shipping losses dropped sharply in 1943 as those of the German’s rose, and Allied merchant construction had produced 14 million tons of new shipping by the end of the year.
No longer safe on the surface the
U-boats served the last 18 months of the war operating as true submarines, unable to pose a real threat to Allied shipping.
The U-boats were a spent force and their decimated fleet surrendered 156 vessels to the Allied navies in May 1945. The U-boat arm suffered the most grievous losses of any service during the war. Some 28,000 were killed of a force totalling 40,000; a devastating 70% casualty rate.