 In November 1941 the IJN's Combined Fleet, under Admiral Isoroku Yamamoto, prepared to participate in Japan's initiation of war with the United States by conducting a preemptive strike against the US Navy's Pacific Fleet base at Pearl Harbor, Hawaii.On 22 November, "Sōryū", commanded by Captain Ryusaku Yanagimoto, and the rest of the "Kido Butai" under Vice Admiral Chuichi Nagumo, including six fleet carriers from the First, Second, and Fifth Carrier Divisions, assembled in Hitokappu Bay at Etorofu Island.The fleet departed Etorofu on 26 November and followed a course across the north-central Pacific to avoid commercial shipping lanes.