wells in Borneo on which the Navy relied and also to the Palau and western Caroline Islands where the Japanese expected the next American attack. However, the location lacked an airfield on which to train the green pilots and American submarines were very active in the vicinity which restricted the ships to the anchorage. Battle of the Philippine Sea The Japanese fleet was en route to Guimaras Island in the central Philippines on 13 June, where they intended to practice carrier operations in an area better protected from submarines, when Vice Admiral Jisaburō Ozawa learned of the American attack on the Mariana Islands the previous day. Upon reaching Guimaras, the fleet refuelled and sortied into the Philippine Sea where they spotted Task Force 58 on 18 June. The Americans failed to locate Ozawa's ships that day and the Japanese turned south to maintain a constant distance between them and the American carriers as Ozawa had decided on launching his air strikes early the following morning. At this time, Air Group 652 consisted of 81 Zeros, 27 D3As, 9 Yokosuka D4Y "Judy" dive bombers and 18 Nakajima B6N "Jill" torpedo bombers, roughly evenly divided among the three ships. The three carriers launched multiple air strikes against the American ships, but generally failed to locate them and did not inflict any damage while losing most of their aircraft. At dusk, the Japanese turned away to the northwest to regroup and to refuel and the Americans turned west to close the distance. They discovered the retiring Japanese fleet during the afternoon of the following day and Vice Admiral Marc Mitscher ordered an air strike launched. Hiyō was struck by two bombs, one of which detonated above the bridge and killed or wounded virtually everyone there. More seriously, the ship was struck by one torpedo dropped by a Grumman TBF Avenger from . This knocked out the starboard engine room and started fires, but Hiyō was able to continue, albeit at a slower speed. Two hours later, a large explosion occurred when leaking gasoline vapor ignited and it knocked out all power on the ship. The fires raged out of control and Hiyō sank stern first shortly afterwards at . Roughly 1,000 men were rescued by her escorting destroyers, but 247 officers and enlisted men died aboard the carrier. Jun'yō was hit by two bombs near her island. The ship was not badly damaged,