Short story German Mighty U-boat

U-boat is the anglicized version of the German word U-Boot [ˈuːboːt] , itself an abbreviation of "Unterseeboot," (meaning in English, "undersea boat"), and refers to military submarinesoperated by Germany, particularly in World War I and World War II. 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 islands of Great Britain and (during World War II) to the Soviet Union and the Allied Countries in the Mediterranean. Austro-Hungarian submarines of World War I (and before) were also known as U-boats.
The distinction between U-boat and submarine is common in several languages, including English (where U-boat refers exclusively to the German vessels of the World Wars) but is unknown in German, in which the term U-Boot refers to any submarine.

The first submarine built in Germany was the two man submarine Brandtaucher, which sank to the bottom of Kiel harbor during its first test dive. The vessel was designed in 1850 by theinventor and engineer Wilhelm Bauer and built by Schweffel & Howaldt in Kiel for the Imperial German Navy. Brandtaucher was later rediscovered during dredging operations in 1887, and subsequently raised sixteen years later and placed in a museum in Germany, where it remains today.

 This was followed in 1890 by W1 and W2, built to a Nordenfelt design. In 1903, Germaniawerft dockyard in Kiel completed Germany's first fully functional submarine, Forelle which was sold to Russia during the Russo-Japanese War in April 1904. The first works were carried out by the Spanish engineer Raymondo Lorenzo d'Equevilley Montjustin (submarine Narval), who based the German Navy's first U-boat design, U-1 on the Russian export models bound for the Russo-Japanese War. U-1 was commissioned into the Imperial German Navy on 14 December 1906. This was based on the Karp-class which had a double hull, was powered by a Körting kerosene engine and armed with a single torpedo tube. It was designated U-1, with the 50% larger U-2 design having two tubes. A diesel engine was not installed in a German Navy boat until the U-19-class of 1912–13. At the start of World War I, Germany had 48 submarines of 13 classes in service or under construction. Germany's first U-boat, U-1, was retired in 1919, and is currently on display at the Deutsches Museum in Munich.