damage control procedures. At midnight, the ships were fueled. Reportedly, in secret defiance of orders to provide the ships with only just enough fuel to reach Okinawa, the Tokuyama personnel actually gave Yamato and the other ships almost all of the remaining fuel in the port, although this probably still was not enough to allow the force to return to Japan from Okinawa. Yamatos executive officer organised a party for the crew for the evening of 5 April, during which many of the officers and sailors drank heavily. The United States Navy was able to monitor preparations for Operation Ten-Go by decoding Japanese radio signals. Through this source, the Americans received conclusive intelligence on 5 and 6 April that the attack was to be attempted. The commander of the United States Fifth Fleet, Admiral Raymond Spruance, ordered his forces to prepare to attack the Japanese at 12:30 am on 6 April, before Yamato and her consorts sailed. Prelude At 16:00 on 6 April, Yamato (with Admiral Itō on board), the light cruiser , and eight destroyers (Asashimo, Hamakaze, Isokaze, Suzutsuki, Hatsushimo, Yukikaze, Fuyutsuki, and Kasumi) 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 on 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. At dawn on 7 April, the Japanese force passed the Ōsumi Peninsula into the open ocean heading south from Kyūshū toward Okinawa. They shifted into a defensive formation, with Yahagi leading Yamato and the eight destroyers deployed in a ring around the two larger ships, with each ship from each other and proceeding at . One of the Japanese destroyers, Asashimo, developed engine trouble and turned back. U.S. reconnaissance aircraft began to shadow the main force of ships. At 10:00, the Japanese force turned west to make it look like they were withdrawing, but at 11:30, after being detected by two American PBM Mariner flying boats, the Yamato fired a salvo with her bow guns using special , but could not prevent the two planes from shadowing the Japanese force. Then they turned back towards Okinawa. Upon receiving contact reports early on 7