British Prime Minister Winston Churchill said there was only one campaign of the Second World War that gave him sleepless nights, that was the Battle of the Atlantic.

The Battle began on 3 September 1939 and lasted 2074 days until 8 May 1945, when Germany surrendered. With over 70,000 allied seamen killed, lost on 3,500 merchant vessels and 175 warships. This was the longest continuous campaign of the war.

Matched against them was the Kreigsmarine. While German surface ships would sally out, this campaign is known for the u-boats that would prey upon allied convoys.

Joining me today is Brian Walter, a retired army officer, recipient of the Excellence in Military History Award from the US Army Center for Military History and the Association of the United States Army. Brian is the Author of The Longest Campaign: Britain's Maritime Struggle in the Atlantic and Northwest Europe, 1939-45.