Although the phrase was not used, by November 1939 the BdU was practicing unrestricted submarine warfare. Neutral shipping was warned by the Germans against entering the zone which, by American neutrality legislation, was forbidden to American shipping, and against steaming without lights, zigzagging or taking any defensive precautions. The complete practice of unrestricted warfare was not enforced for fear of antagonising neutral powers, particularly the Americans. Admirals Raeder and Dönitz and the German Naval Staff had always wished and intended to introduce unrestricted warfare as rapidly as Hitler could be persuaded to accept the possible consequences.