U-Boot is the German term for generically submarines, and is the abbreviation for Unterseeboot, literally "submarine boat". The term is used in other languages to indicate submarine and submarine boats used by the German navy (Kaiserliche Marine and Kriegsmarine) during the first and second world wars.
The anglicized form U-Boat is sometimes used.
The targets of U-boat campaigns in both conflicts were convoys carrying supplies from the United States and Canada to Europe.
The term U-Boot, followed by a number, for example U-Boot 47 indicates a specific vessel, while U-Boot Type II a certain class. The only U-boats that can be considered real submarines, and not submarines, are those belonging to Type XXI and Type XXIII.
The post-war Deutsche Marine submarines are U-boats and continue to have the U-boat designation, for example U-Boot-Klasse 212 A.
16 submarines, captured during World War II, were then in service in the Kriegsmarine as U-boats.
Several German U-boats were in service, in the first years following World War II, in various navies by way of war reparations.
The term U-boat can indicate in other languages, other than German, the following types of submarines:
the German submarines of the Kaiserliche Marine of the First World War;
the Austro-Hungarian submarines of the k.u.k. Kriegsmarine of the First World War;
the German submarines of the Kriegsmarine of the Second World War;
the German submarines of the Bundesmarine after World War II;
the German submarines of the Deutsche Marine after German reunification.
First World War
In May 1915, the German U-20 (U-Boot Type U 19) sank the ocean liner RMS Lusitania. Of the 1,345 victims, 127 were American civilians, including a well-known theater producer and a member of the Vanderbilt family. The event turned American public opinion against Germany and was a major factor in the United States' entry into the war alongside the Allies during the First World War.
On January 31, 1917, Germany declared that its U-boats would engage in indiscriminate submarine warfare.
World War II
During World War II, U-boat attacks were the main component of the Battle of the East North Atlantic, which lasted until the end of the war. During the early stages of the war and soon after the entry of the United States, U-boats were extremely effective in destroying Allied merchant ships. The improvements in convoys tactics, sonar, depth bombs, the deciphering of the Enigma Code used by the Germans and the range of the escort planes served to turn the tide against the U-boats. Eventually the U-boat fleet suffered extremely heavy losses, losing 789 units (plus 3 captured British submarines) out of 1,157 (including 25 Allied captured) and about 30,000 sailors out of a total of 50,000. In addition, Germany possessed 700 very small submarines. It should be remembered the help of the Italian submarines, who helped the German ally with 32 units and 109 ships sunk. The German U-boats and the Japanese and Italian submarines sank a total of 2828 Allied ships, for a total of about 15 million tons. Between 1939 and 1942 the U-boats sank various cargo ships passing along the American West Coast almost undisturbed, causing extensive damage. When the British found a way to decipher Enigma and the allies were able to predict the movements of the U-boats, the Germans did not stop their use in the Atlantic.
During the Second World War, the Kriegsmarine (the German Navy) produced different types of U-boats as technology improved.