German submarine U-4 (1935)

German submarine U-4 was a Type IIA U-boat of Nazi Germany's Kriegsmarine before and during World War II. She was one of the longest lasting German submarines of the period, primarily since half of her time was spent on training duties in the Baltic Sea. Commissioned on 17 August 1935, she was one of the first batch of Type IIA boats constructed following the Anglo-German Naval Agreement that repealed the terms of the Treaty of Versailles which ended the First World War and stated that Germany was not permitted to possess submarines. Built at the Deutsche Werke in Kiel as yard number 239, she was a highly sought after command before the outbreak of the Second World War in 1939. Once the war had begun however, she rapidly became obsolete. Before she was superseded, she carried out four combat patrols, mainly in support of the Norwegian campaign. She was the most successful Type IIA boat by tonnage of shipping sunk, sinking three freighters and one submarine for 5,133 GRT and 1,090 tons, respectively.