 Admiral Isoroku Yamamoto issued the code phrase " Niitaka yama nobore " ( Climb Mount Niitaka ) on 2 December 1941 from Nagato at anchor at Hashirajima to signal the 1st Air Fleet ( Kido Butai ) to proceed with its attack on Pearl Harbor . When Japan began the Pacific War on 8 December , the sisters sortied for the Bonin Islands , along with the four ships of Battleship Division 2 and the light carrier Hōshō as distant cover for the fleet attacking Pearl Harbor , and returned six days later . Yamamoto transferred his flag to the new battleship Yamato on 12 February 1942 . 
