The Battle of Atlantic lasted as long as WWII itself, 1939-1945, however, it was most significant from mid-1940 to the end of 1943. To survive the war against Hitler’s forces, Britain needed imports of food, fuel and raw materials from overseas. America provided Britain with the only tools needed for its success as Britain’s successful defence ensured that there was a base for Western Allies to launch a strategic air offense or a land invasion of the Europe mainland to defeat Germany.


  • September 3 1939 Britain declared war on Germany and British liner Athenia was torpedoed by a U-boat
    • British then forced to provide convoys with naval escorts for long journey

o   From Halifax convoys of ships were sent out to head across the Atlantic to Europe.

o   From the New York to Britain route, the ships ran 10 knots for 15 days, however after the U-Boat blockade the ships ran at 7½ knots for 19 days from Freetown on West African Coast.


  • Between Jan 1 and March 31, 108 ships (343,610 tons of shipping sunk)
  • British building capacity was 200,000 tons per month
  • March 4 31 U-Boats sent for the invasion of Scandinavia. The U-Boats had a far larger scope once the duration of the war progressed. During this invasion, the Allies made the lowest losses to the U-Boats (20 ships, only 88,000 tons)
  • May 15 preceding of Lend-Lease began where 40-50 destroyers were given by President Roosevelt to Britain in compensation for the Guiana, Antiles, Bermuda, Bahamas to US. This strengthened America’s military security as the ‘great arsenal of democracy’ aided Britain without being involved in the war.
  • June to August 58 ships sunk (284,113 tons of shipping sunk)
  • After gaining Norway, Holland, Belgium, North France (June) 140 ships were sunk (585,496)
  • German building eight U-boats for every one lost.
  • September 1 57 U-Boats (same number as they began the war with)
  • U-boats along with mines, aircraft and surface ships, succeeded in destroying three million tons of Allied shipping between Fall of France in June 1940 and end of the year
  • Admiral Donitz, commander of U-boat arm introduced the ‘wolfpack’ tactic at the end of 1940 where group of submarines would surface and attack at night, reducing effectiveness of ASDIC and communication by radios
  • British developed their tactics

o   Corvettes, small warships of less than 1000 tons, helped to plug the gaps in the Royal Navy’s escort capability and Allied occupation of Iceland gave Britain some valuable Atlantic bases

Atlantic Gap

  • Vast stretches of the Atlantic could not be patrolled by air – ‘A mid-Atlantic gap’ (left merchant ships unprotected for a large part of the ocean)

o   Light escort carriers capable of carrying aircraft entered service in September 1941

o   Fighter aircraft such as ‘Hurricane’ could be carried to mid-Atlantic and catapulted from decks of specially adapted ships (Catapult Aircraft Merchant Ships) but the planes had to get ditched in the sea afterwards (‘one-shot weapons’)

The Crisis (early 1943)

  • Donitz, commander of Germany Navy, had 200 operational U-boats
  • British supplies especially oil were running out and became the question of whether Allied shipyards could build merchant ships fast enough to replace the tonnage that was being sunk

o   Mass production of Liberty ships in US shipyards, helped to ensure that the Allies would win this race

  • Better weapons and radio, long-range aircraft Liberator being equipped with centimetric radar

o   Allowed for the detection of much smaller objects and the use of much smaller antennas

  • Allied sinking of German submarines began to escalate, with 45 being destroyed in months of April and May

o   Donitz called off battle on May 23 1943

  • Between 75000 and 85000 Allied seamen were killed
  • About 28000 out of 40000 U-boat were killed during World War Two and some two-thirds of these died in the course of the battle


  • In the Norwegian invasion, torpedoes were used, which showed its unreliability. Commander Günter Prien of the U-47 fired 8 torpedoes and “that it was useless to send him to fight with a dummy rifle”. As a result of the torpedoes, an entire squadron Battleship called Warspite was saved (7 cruisers, 7 destroyers, 5 transports)
  • In early stages of battle the Royal Navy relied on ASDIC (device using sound waves underwater) to detect submerged U-boats

o   Sunk pocket battleship of Graf Spee in December 1939 and battleship Bismarck in 1941

  • Royal Navy captured an Enigma machine from U-boat in 1941 and was able to break Enigma Codes

o   Knew where U-boats were patrolling and thus, British able to move convoys in safe areas away from wolfpacks

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