Also on 15 June, the Japanese First Mobile Fleet under Vice Admiral Ozawa Jisaburo emerged from the Philippines through the San Bernardino Strait and headed northeast in Operation a-go, which was intended to draw the U.S. fleet into a decisive battle that would reverse the course of the war in the Central Pacific. Assembled over the preceding month, Ozawa's force comprised 90 percent of Japan's surface naval strength and consisted of 5 fleet carriers, 4 light carriers, 5 battleships, 11 heavy cruisers, 2 light cruisers, 28 destroyers, and 473 aircraft. Ozawa believed his inferior aircraft numbers would be offset by the greater range of his planes and by the presence of 90 to 100 land-based aircraft on the islands of Guam, Yap, and Rota, with which he planned to attack the U.S. carriers to initiate the battle. As Ozawa's own carriers came into range, his planes would launch a second strike, refuel and rearm on the islands, and then attack the Americans a third time while returning to the Japanese fleet.
The U.S. submarine Flying Fish reported the Japanese sortie from the Philippines. Leaving his older battleships and several cruisers and destroyers to protect the Saipan beachhead, Spruance joined Mitscher's Task Force 58 on 18 June to search for Ozawa. Misled by the commander of the Japanese land planes and unaware that most of them had been destroyed by attacks from Mitscher's undamaged carriers, Ozawa launched four attack waves on the morning of 19 June, only to lose 346 planes in what the victors called the "Great Marianas Turkey Shoot." That same day, the U.S. submarine Albacore sank the Taiho, Japan's newest and largest carrier and Ozawa's flagship; another submarine, the Cavalla, sank the Japanese fleet carrier Shokaku.
Spruance still did not know Ozawa's precise location, and he rejected Mitscher's urging that he move offensively toward the west for fear that the Japanese might flank him and get between him and the Saipan landing sites. Aerial night searches were deemed impractical because aircrews were exhausted and the moon was new. Although Mitscher dispatched extensive search missions through the morning and early afternoon of 20 June, not until 4:00 p.m. were Ozawa's ships finally sighted, at the extreme range of the U.S. aircraft. Despite his realization that his planes would return to their carriers in darkness and that many of them would probably exhaust their fuel beforehand, Mitscher ordered a massive strike. It found Ozawa's ships shortly before dark and sank another fleet carrier, the Hiyo, and 2 oilers; severely damaged 3 other carriers, a battleship, a heavy cruiser, and a destroyer; and eliminated all but 35 of the remaining Japanese aircraft.
The return flight of the U.S. aircraft became one of the most dramatic episodes of the Pacific war. Only 20 of the 216 aircraft sent out earlier had been lost in action, but 80 were lost in ditchings or crash landings. Ignoring the risk of Japanese submarines, Mitscher ordered his carriers to turn on all their lights to guide his fliers, and efficient search-and-rescue work recovered all but 49 airmen. Spruance pursued the retreating Japanese from midnight to the early evening of 21 June, but he was slowed by his destroyers' need to conserve fuel, whereas Ozawa accelerated the withdrawal begun after his losses on 19 June.
Although it effectively destroyed Japanese naval air power, the Battle of the Philippine Sea quickly became controversial; members of Mitscher's staff condemned Spruance for not steaming farther westward on the night of 18–19 June to give Mitscher a more favorable launch position. Mitscher, for his part, was criticized for not sending out night searches on 19–20 June that might have found Ozawa sooner and allowed the Americans more daylight for their air attack on the Japanese fleet, perhaps even creating conditions for a surface engagement. Such a scenario, however, might have resulted in much greater losses for the U.S. side with no more strategic benefits than were actually gained. John A. Hutcheson Jr.
Dull, Paul S. A Battle History of the Imperial Japanese Navy (1941–1945). Annapolis, MD: Naval Institute Press, 1978.; Morison, Samuel Eliot. History of United States Naval Operations in World War II. Vol. 5, The Struggle for Guadalcanal, August 1942–February 1943. Boston: Little, Brown, 1949.; Spector, Ronald H. Eagle against the Sun: The American War with Japan. New York: Vintage Books, 1985.; Y'Blood, William T. Red Sun Setting: The Battle of the Philippine Sea. Annapolis, MD: Naval Institute Press, 1981.
John A. Hutcheson Jr.