At 16:00 on 6 April, "Yamato", with Admiral Itō on board, the light cruiser and eight destroyers departed Tokuyama to begin the mission.Two American submarines, and , sighted the Japanese force as it proceeded south through the Bungo Channel. Although they were unable to attack (due to the ships' speed), they did spend several hours shadowing the Japanese sortie and sending updates of its course to the U.S. fleet. The submarines' messages, which were reportedly sent uncoded, were also picked up by radio operators on the Japanese ships.