In May 1940, it looked like the deadly 'wolf packs' of German U-boats would sever Britain's Atlantic lifeline and force her to surrender.

In 1941 the Atlantic convoys slowly began to fight back, using cutting-edge technology that turned the German U-boat hunters into the hunted.

In December 1941 the surprise Japanese attack on Pearl Harbor brought the USA into the Second World War. With the help of America, Britain hoped her fortunes would change in the Atlantic and the German U-boats would be defeated. But America refused to adopt the convoy system to protect merchant ships carrying vital supplies to Britain, and as a result suffered its single greatest ever naval defeat.

By January 1943, the Allies had developed technology and tactics that could take on the German U-boat threat. But an area of the mid-Atlantic, out of the range of Allied aircraft, was being targeted by the U-boats hunting convoys. So America introduced the long-range Liberator bomber in an attempt to close the air gap and win the war in the Atlantic. And Germany sent U-boats into the English Channel, hoping they could play a crucial role in preventing the D-Day landings.