German submarine U-1 was the first U-boat (or submarine) built for the German Kriegsmarine following Adolf Hitler's abrogation of the terms of the Treaty of Versailles in 1935, which banned Germany possessing a submarine force. A Type IIA U-boat, she was built at the Deutsche Werke shipyards in Kiel as 'Werk' 236, her keel being laid on 11 February 1935 amid celebration. She was completed on 29 June 1935 after a very rapid construction, and was manned by crews trained in the Netherlands.