Second World War - Arctic & Atlantic Oceans
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From 3 September 1939, the outbreak of war, Britain's Royal Navy blockaded the short north-west coast of Germany and penned up the small German navy. Although Germany possessed only four battleships and one aircraft carrier, she had almost a hundred U-boat submarines. So German policy became to attack Allied commercial and naval shipping with U-boats, while deploying her few but powerful surface ships as raiders in the open sea. The North Atlantic was the main theatre of action as an isolated Britain, cut off from commerce with Occupied Europe, tried to sustain herself with goods and war materials from Canada and the United States, and from her colonies further afield.

Those colonies also provided many thousands of seamen for the Merchant Navy, volunteers and experienced men alike. Nearly 60,000 Indian merchant seamen served the Allied cause during the Second World War, and several thousand Africans and men from the Caribbean, too. Unable to fight back as they sailed on unarmed ships transporting all manner of dangerous, often explosive cargoes, the target of German surface raiders and U-boats, such men were the incredibly brave backbone of the long, ultimately successful struggle to keep Britain and Europe supplied with materials for war and for everyday life. Around 30,000 merchant seamen, including many West Indians and Indians, died during this long-drawn-out Battle of the Atlantic, as well as many thousand service personnel.

On the very first day of the war the British passenger liner Athenia was torpedoed and sunk in the Atlantic with the loss of 112 lives. By the end of 1939 U-47 had sunk the battleship Royal Oak (786 died), and the battle was well and truly on. In 1940 two German surface raiders, the pocket battleship Admiral Scheer and the heavy cruiser Hipper, began operating in the North Atlantic.

In 1941 Allied convoys were attacked by U-boats operating in 'wolf packs' and by long-range bombers from occupied Norway and France. By June nearly 6 million tons of shipping had been sunk - most of it in mid-Atlantic, where escorting British aircraft did not yet have the range to operate. The German battlecruisers Scharnhorst and Gneisenau had success as surface raiders early in the year, as did Hipper on a February-April cruise from Brest. But in May the pocket battleship Bismarck was sunk after an epic chase. In August, a few weeks after Germany invaded Russia, Allied convoys commenced running to the Arctic port of Murmansk. These Arctic convoys proved particularly unpleasant due to the cold, the rough seas and the constant danger from air and sea attack. In the same month, US warships began escorting North Atlantic convoys as far as Iceland, where Allied air cover could take over.
West Indian Servicemen convoy arrives in Britain, 1944
West Indian Servicemen convoy arrives in Britain
© Imperial War Museum

In February 1942 Scharnhorst, Gneisenau and the heavy cruiser Prinz Eugen took advantage of a thick fog and made a daring escape up the length of the English Channel and into the North Sea. Early in the year, after the US had entered the war, German U-boats had great success against inexperienced American ships. By the end of the year well over a million tons of Allied shipping had been sent to the bottom of the Atlantic. 85 U-boats had gone there too. Slowly but surely the Battle of the Atlantic was turning the Allies' way. But the Murmansk convoy losses continued to mount, the worst being Convoy PQ17 in June-July 1942, when 23 of 37 merchantmen were sunk after the convoy was ordered to scatter just as its escort was withdrawn. Throughout 1943 the Arctic convoys continued, though, and in December of that year Scharnhorst was sunk when she left her Norwegian anchorage to attack Convoy JW55B. Of her 1900 officers and men, only 36 were saved.

U-boats decreased in effectiveness as Allied submarine-hunting techniques improved through 1944. The battleship Tirpitz, always more potent as a threat than an actual weapon, was finally sunk at her Tromso anchorage by RAF bombers on 12 November 1944. By then the Allies were in control of both Atlantic and Arctic. The only major threat thereafter was from minefields and from sporadic torpedo-boat attacks in home waters, and these had ceased by the end of hostilities in May 1945.
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