The term wolf pack refers to the mass-attack tactics against convoys used by U-boats of the Kriegsmarine during the Battle of the Atlantic and submarines of the United States Navy against Japanese shipping in the Pacific Ocean in World War II. Karl Dönitz used the term Rudel to describe his strategy of submarine warfare?Rudel translates best as "pack" of animals and has become known in English as "wolf pack" (Wolfsrudel), a more accurate metaphoric, but not literal, translation. U-boat movements were controlled by the Befehlshaber der Unterseeboote (BdU; English translation: "Commander of Submarines") much more closely than American submarines, which were given tremendous independence once on patrol. Accordingly, U-boats usually patrolled separately, often strung out in co-ordinated lines across likely convoy routes (usually merchants and small vulnerable destroyers), only being ordered to congregate after one l