Plan Z
"U-40" was ordered by the "Kriegsmarine" on 29 July 1936 (as part of Plan Z and in violation of the Treaty of Versailles). Her kneel was laid down on 1 July 1937. "U-40" was launched on 9 November 1938 and commissioned on 11 February 1939 under the command of "Kapitänleutnant" Werner von Schmidt.