Battle of The Philippine Sea - Initial Stages

Initial Stages

On June 12, 1944 U.S. carriers started a series of air strikes on the Marianas, convincing Admiral Toyoda that the U.S. was preparing to invade. This move came as a surprise; the Japanese had expected the next U.S. target to be farther to the south, either the Carolines or the Palaus. Therefore, the Marianas were protected with only 50 land-based aircraft. On June 13, U.S. forces began bombardment operations for invading Saipan; in response, Toyoda ordered a fleet-based counterattack. The main portions of the fleet, consisting of six carriers and several battleships, rendezvoused on June 16 in the western part of the Philippine Sea and completed refueling on June 17.

The Japanese fleet, commanded by Vice-Admiral Jisaburo Ozawa, consisted of five large carriers (Taihō, Shōkaku, Zuikaku, Junyō, and Hiyō), four light carriers (Ryuho, Chitose, Chiyoda, and Zuihō), five battleships (Yamato, Musashi, Kongō, Haruna and Nagato) and supporting cruisers, destroyers, and oilers.

This force was sighted on June 15 by American submarines and by the next day Admiral Raymond Spruance, commander of the U.S. 5th Fleet, was convinced that a major battle was at hand. By the afternoon of June 18, Vice Admiral Marc Mitscher, aboard his flagship (the carrier USS Lexington) had his Task Force 58 (the Fast Carrier Task Force) formed up near Saipan to meet the Japanese attack.

TF-58 consisted of five major groups. In front (to the west) was Vice Admiral Willis Lee's Task Group 58.7 (TG-58.7), the "Battle Line", consisting of seven fast battleships (Washington, North Carolina, Indiana, Iowa, New Jersey, South Dakota and Alabama). Just north of them was the weakest of the carrier groups, Rear Admiral William K. Harrill's TG-58.4 of three carriers (Essex, Langley and Cowpens). To the east, in a line running north to south, were three groups each containing four carriers: Rear Admiral Joseph Clark's TG-58.1 (Hornet, Yorktown, Belleau Wood and Bataan); Rear Admiral Alfred Montgomery's TG-58.2 (Bunker Hill, Wasp, Cabot and Monterey) and Rear Admiral John W. Reeves's TG-58.3 (Enterprise, Lexington, San Jacinto and Princeton). The capital ships were supported by eight heavy cruisers, 13 light cruisers, 58 destroyers, and 28 submarines.

Shortly before midnight on June 18, Admiral Chester W. Nimitz sent Spruance a message from Pacific Fleet Headquarters indicating that the Japanese flagship was approximately 350 miles (562 km) to the west-southwest of Task Force 58. This was stated as based on a "fix" obtained by radio direction-finding, but was more probably due to decryption of intercepted Japanese naval messages.

Mitscher realized that if Task Force 58 were to advance westward, there was a strong chance of a night surface encounter with Ozawa's forces. He therefore conferred with Lee and inquired whether Lee favored such an encounter. The battleship commander was not enthusiastic about a night engagement with Japanese surface forces, despite his new ships outclassing most of the Japanese battleships, feeling that his crews were not adequately trained for such an action. Shortly after his discussion with Lee, Mitscher asked Spruance for permission to head west during the night to reach what would be an ideal launch position for an all-out aerial assault on the enemy force at dawn.

Spruance refused. Throughout the run-up to the battle he had been concerned that the Japanese would try to draw his main fleet away from the landing area using a diversionary force, and would then make an attack around the flank of the U.S. carrier force — an "end run" — hitting the invasion shipping off Saipan. He was therefore not prepared to let Task Force 58 be drawn westward, away from the amphibious forces, as he was aware that Japanese operational plans frequently relied on diversionary forces. On this occasion, however, there was no such aspect to the Japanese plan; there was no ruse and no diversionary force.