More than 5,000 cargo ships were sunk by German U-boats
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Battle of the Atlantic in Liverpool

24 May 2013 Last updated at 16:37 BST

The Battle of the Atlantic was the longest military campaign of World War II - and a battle Britain had to win survive.

From 1940 to the end of 1943, The North Atlantic was the main supply route for trade vessels and warships, many of which sailed in and out of Liverpool.

More than 35,000 allied sailors lost their lives in the battle to protect this vital sea corridor from the German U-boat threat.

Surviving veterans gather in Liverpool over the Bank Holiday weekend (24 to 27 May) to mark the 70th anniversary of this war of attrition between the convoys and the U-boats.