Henning Rudolf Adolf Karl von Holtzendorff was a German admiral during World War I, who became famous for his December 1916 memo about unrestricted submarine warfare against the United Kingdom. He was a recipient of Order of the Black Eagle and the Pour le Mérite with oak leaves and was one of just six Grand Admirals of the Imperial German Navy.
Admiral von Holtzendorff in 1918
Vice Admiral von Holtzendorff in 1906
Submarine warfare is one of the four divisions of underwater warfare, the others being anti-submarine warfare, mine warfare and mine countermeasures.
British WWI propaganda poster
Grand Admiral Erich Raeder with Otto Kretschmer (left), a German U-boat commander, August 1940