According to the book "German submarines secret 1935-1945" put author and publisher before another documentary about the development of the empire and navy. Based on the documentation provided by the Main Office of warships - it had its headquarters in Berlin Shell House at Abwehr headquarters - the public, the author now with files on the construction of surface vessels of the Imperial Navy and known. As with the documentation on the submarines of the band is equipped with the originality of the shipyard photos and other material.