U-boats were naval 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) and 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 and other parts of the British Empire, and from the United States, to the United Kingdom and (during the Second World War) to the Soviet Union and the Allied territories in the Mediterranean. German submarines also destroyed Brazilian merchant ships during World War II, causing Brazil to declare war on both Germany and Italy on 22 August 1942. The term is an anglicised version of the German word U-Boot , a shortening of Unterseeboot (under-sea boat), though the German term refers to any submarine. Austro-Hungarian Navy submarines were also known as U-boats. Early U-boats (1850–1914) The first submarine built in Germany, the three-man Brandtaucher, sank to the bottom of Kiel Harbor on 1 February 1851 during a test dive. Inventor and engineer Wilhelm Bauer had designed this vessel in 1850, and Schweffel and Howaldt constructed it in Kiel. Dredging operations in 1887 rediscovered Brandtaucher; she was later raised and put on historical display in Germany. The boats Nordenfelt I and Nordenfelt II, built to a Nordenfelt design, followed in 1890. In 1903, the Friedrich Krupp Germaniawerft dockyard in Kiel completed the first fully functional German-built submarine, Forelle, which Krupp sold to Russia during the Russo-Japanese War in April 1904. The was a completely redesigned and only one was built. The Imperial German Navy commissioned it on 14 December 1906. It had a double hull, a Körting kerosene engine, and a single torpedo tube. The 50%-larger (commissioned in 1908) had two torpedo tubes. The class of 1912–13 had the first diesel engine installed in a German navy boat. At the start of World War I in 1914, Germany had 48 submarines of 13 classes in service or under construction. During that war, the Imperial German Navy used SM U-1 for training. Retired in 1919, she remains on display at the Deutsches Museum in Munich. World War I (1914–1918) On 5 September 1914, was sunk by , the first ship to have been sunk by a submarine using a self-propelled torpedo. On 22 September, under the command of