As the European war grew into a global war in 1941 more and more fighting took place at sea, especially the Atlantic Ocean, between the British and German navies. The aim of the Germans was to sink ships taking food and raw materials to Britain, and so starve the British into surrender. The aim of the British was to keep their shipping routes open at all costs.

Up to 1941 there were no great sea battles between the German and British fleets. German warships concentrated their attacks on British merchant shipping and did not try to confront the Royal Navy. The only major sea battle in the early stage of the war took place in December 1939, when three British warships trapped the German pocket battleship Graf Spee in the River Plate in South America, forcing the ship's captain to scuttle her.

In May 1941 the Germans decided to create a squadron of powerful warships based in the occupied French port of Brest. Their aim was to attack British convoys deep in the Atlantic. This meant bringing their only battleship, the Bismarck, and the battlecruiser Prinz Eugen from the Baltic Sea to the Atlantic to join the cruisers Gnetsenau and Scharnhorst that were already active there.

The two ships sailed out of the Baltic on 18 May but a British aircraft spotted them as they sheltered in a fjord in Norway. A Royal Navy fleet of seventeen ships was sent to chase them. When they engaged the German ships in battle on 24 May, a single shot from the Bismarck penetrated the weak deck armour of HMS Hood and blew it up, killing all but three of its 1400 crew.

The British sent all their available warships to hunt the Bismarck as it escaped into the Atlantic. On 26th May, a torpedo from one of the carrier Ark Royal's aircraft damaged the Bismarck's steering gear, forcing it to drop speed. On 27 May British ships caught up with the Bismarck and destroyed her with gunfire and torpedoes. The blazing wreck went to the bottom with all but 110 of its 2300 crew.

The Prinz Eugen, meanwhile, had escaped the British ships and was able to join the Scharnhorst and Gnetsenau in Brest. The three ships made many attacks on British shipping from there before returning to the safety of the Baltic in March 1942.