A torpedo is self-propelled underwater missile launched from a tube located on the deck or inside the hull of a warship. The man who invented the first torpedo was Captain David Bushnell, who tried it out in New York Harbour in 1776. Bushell named it after the torpedo fish, a ray with an electric apparatus for killing its prey. Bushnell's torpedo comprised an explosive charge fixed to an enemy hull and was set-off by a clockwork fuse. These early torpedoes were stationary devices which exploded against vessels and were later classified as mines.

The first automatic torpedo was produced in 1868 by the English engineer, Robert Whitehead. This engine driven torpedo travelled at speeds of 15 to 20 knots. The device was self-propelled through compressed air. The British first starting buying Whitehead's torpedoes in 1871. By 1881 Whitehead's customers included Austria, Germany, France, Italy, Russia, Argentina, Belgium, Denmark, Greece and Portugal. The first time one of Whitehead's torpedoes were used during a war was on 25th January 1878, when the Russian navy sank a Turkish steamer.

Torpedo tubes were first built into submarines in 1885 by the Swedish armaments manufacturer, Thortsen Nordenfelt. The German Navy was the first to fire an automotive torpedo. On 8th August 1914 a German U-boat unsuccessfully attacked the British battleship Monarch.

Torpedoes in 1914 carried a contact-triggered explosive warhead and had a range of 10,000 metres and could travel at 41 knots. However, their ideal range was about a kilometre because they tended to be inaccurate over longer distances. The fear of torpedoes meant that most large battleships were kept at home during the First World War. The were therefore mainly used against ships transporting troops and supplies.