U-boat is the anglicised version of the German word U-Boot [ˈuːboːt], a shortening of Unterseeboot, literally "undersea boat". While the German term refers to any submarine, the English one (in common with several other languages) refers specifically to military submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare role (commerce raiding), enforcing a naval blockade against enemy shipping. The primary targets of the U-boat campaigns in both wars were the merchant convoys bringing supplies from Canada, the British Empire, and the United States to the United Kingdom and (during the Second World War) to the Soviet Union and the Allied territories in the Mediterranean.

Austro-Hungarian navy submarines were also known as U-boats.

Pre-War

The first submarine built in Germany was the three-man Brandtaucher, which sank to the bottom of Kiel harbor during its first test dive. The vessel was designed in 1850 by the inventor and engineer Wilhelm Bauer and built by Schweffel & Howaldt in Kiel. Brandtaucher was later rediscovered during dredging operations in 1887, and raised sixteen years later and placed in a museum in Germany.

U-boat (German: U-Boot) is a German military submarine of World War I and II.

U-boat or U-Boot may also refer to:

The Spy in Black (US: U-Boat 29) is a 1939 British film, and the first collaboration between the British filmmakers Michael Powell and Emeric Pressburger. They were brought together by Alexander Korda to make the World War I spy thriller by Joseph Storer Clouston into a film. Powell and Pressburger eventually made over 20 films during the coursde of their partnership.

The Spy in Black stars Conrad Veidt, Valerie Hobson, Sebastian Shaw and features Marius Goring.

Plot

Captain Hardt (Conrad Veidt), a World War I German U-boat commander, is ordered to lead a mission to attack the British Fleet at Scapa Flow. He sneaks ashore on the Orkney Islands to meet his contact, Frau Tiel (Valerie Hobson). Tiel has taken over the identity of local schoolteacher, Anne Burnett (June Duprez), who had been kidnapped by German agents. Hardt finds himself attracted to her, but Tiel shows no interest. The Germans are aided by a disgraced Royal Navy officer, the former Commander Ashington (Sebastian Shaw) who, according to Tiel, has agreed to aid the Germans after losing his command due to drunkenness, and Tiel implies that she has slept with Ashington to obtain his cooperation.