Key point: The Japanese losses were irreplaceable.
The Philippine Sea encompasses two million square miles of the western part of the Pacific Ocean. It is bounded by the Philippine Islands on the west, the Mariana Islands on the east, the Caroline Islands to the south, and the Japanese Islands to the north. In the summer of 1944 it was the battleground of two great carrier strike forces. One of these belonged to Japanese Vice Admiral Jisaburo Ozawa. The other belonged to U.S. Admiral Raymond Spruance, and its carriers were under the tactical command of Marc Mitscher. Ozawa had explicit orders to halt the steady advance of the U.S. 5th Fleet, to which Mitscher’s carriers belonged, across the vast Pacific Ocean toward Japan.
Ozawa had the majority of the Imperial Japanese Navy’s fighting fleet under his command at the time, but his force of approximately 90 ships and submarines was still considerably smaller than the U.S. Navy’s 129 ships and submarines. He also commanded 450 carrier-based aircraft that would coordinate with 300 ground-based aircraft in the Marianas.
Ozawa’s strike force steamed east in two groups. The vanguard, comprising three small carriers, four battleships, and other vessels, plowed through the Philippine Sea 100 miles ahead of the main group, which was composed of six large carriers, a battleship, and a wide array of supporting vessels.
Ozawa’s strategy was simple. His vanguard would serve as a decoy to lure the U.S. carrier aircraft while the aircraft from the main group, reinforced with land-based aircraft in the Marianas, inflicted heavy damage in multiple attacks.
Ozawa had no intention of letting Mitscher land the first blow. Japanese carrier aircraft had greater range than U.S. carrier aircraft, and Ozawa planned to make the most of his advantage. In addition, Ozawa would be able to launch his aircraft into the wind. The U.S. carriers would have to turn around and sail away from the Japanese fleet to launch their aircraft into the wind.
The Trap Flops for Ozawa
What Ozawa did not know was that even before he launched his aircraft on June 19, Mitscher had derailed his plan by knocking out the Japanese ground-based aircraft in the Marianas more than a week earlier. Beginning on June 11, Mitscher had sent his aircraft against Japanese air bases on the islands of Guam, Saipan, and Tinian in the Marianas. Sweeps in the days afterward pummeled the targets repeatedly to ensure aircraft were destroyed and airstrips too damaged to use. When the battle did start, Mitscher would enjoy a two to one advantage in aircraft. Rather than Mitscher sailing into a trap, it was Ozawa who was sailing into one.
Following the American defeat at Pearl Harbor in December 1941, the U.S. Navy had moved decisively toward establishing the world’s first carrier-centered navy, a force that would play a deciding part in the Allied victory at Midway in June 1942.
In revenge for the surprise attack on Pearl Harbor on December 7, 1941, U.S. carrier aircraft struck back in the Battles of the Coral Sea and Midway. The Japanese failure to win a decisive victory in the Coral Sea, coupled with their loss at Midway, only strengthened the Japanese dependence on the strategy of a defensive decisive victory.
Uncertainty Grows for the Japanese High Command
Meanwhile at Midway, Spruance, who had no earlier experience with carrier-launched aircraft battles, commanded Task Force 16, including the carriers Enterprise and Mitscher’s Hornet. Despite his inexperience, he was able to oversee an American victory, which included the sinking of four Japanese carriers.
The Americans leapfrogged their way steadily north through the South Pacific, and the Japanese worked to build up their navy, waiting and watching for an opportunity for kantai kessen, the battle they believed would lead to the destruction of American naval power and decide the rest of the war. That opportunity, they would finally decide, had come in June 1944 in the Philippine Sea.
By 1944, however, the Japanese high command feared its ability to fight and win such a kantai kessen battle was slipping away. Imperial Navy aircrews had suffered serious losses, especially of skilled pilots at Coral Sea, Midway, and during the Solomon Islands campaigns. These were losses they could not easily replace, while the United States could easily replace its losses.
By the summer of 1944, the Americans had worked their way north sufficiently that they were preparing to invade the Mariana Islands. The Marianas, situated 700 miles south of the Japanese home islands, controlled the sea lanes to Japan. The capture of the islands would give the United States control of these sea lanes and would also put the U.S. Boeing B-29 Superfortress heavy bombers within striking distance of the Japanese home islands. Japan had to prevent the loss of the Marianas and stop the American advance north.
Mitscher’s Task Force 58
Still looking for the decisive victory that might end the war in the Pacific, the Japanese began eyeing Mitscher’s Task Force 58. The task force comprised five attack groups, each composed of three or four carriers and supporting ships. The ships of each attack group sailed in a circle formation with the carriers in the center and the supporting ships sailing close to the carriers so they could add their antiaircraft fire to that of the carriers and help ward off any attacking aircraft. When under attack by torpedo aircraft, the task group would turn toward the oncoming aircraft to limit attack angles. In addition, the carriers would not take evasive action when under attack, which allowed more stable platforms for the antiaircraft fire of all the ships in the task group. Mitscher had introduced many of these tactics.
In June 1944, Task Force 58 was part of Spruance’s 5th Fleet. The ships at sea were designated Task Force 58 under Spruance and Task Force 38 under Admiral William Halsey. The six-month name changes and apparent shifting of personnel in this two-platoon system had some benefit in confusing the Japanese, who at times were unsure as to the actual size of the American force.
Admiral Mineichi Koga, commander of the Combined Japanese Fleet, had been killed in March 1944 when his plane crashed in a typhoon. He was replaced with Admiral Soemu Toyoda, a torpedo and naval artillery expert who had been opposed to war with the United States, a war he had considered unwinnable. Despite this belief, Toyoda continued to develop the attack plans that Koga had been working on, plans aimed at a decisive victory.
The Japanese Fleet Rendezvous in the Philippine Sea
On June 11, Mitscher’s carriers launched their first air strikes on the Marianas, and Toyoda became aware that the showdown in the Central Pacific was at hand. Japan had to save Saipan, and the only possible defense, he believed, was to sink the U.S. 5th Fleet that was covering the landing.
The Japanese fleet Ozawa commanded consisted of three large carriers (Taiho, Shokaku, and Zuikaku), two converted carriers (Junyo and Hiyo), and four light carriers (Ryuho, Chitose, Chiyoda, and Zuiho). Ozawa’s fleet also included five battleships (Yamato, Musashi, Kongo, Haruna, and Nagato), 13 heavy cruisers, six light cruisers, 27 destroyers, six oilers, and 24 submarines. Ozawa commanded from aboard the Taiho, which was the first Japanese carrier to have been built with an armor-plated flight deck, which was designed to withstand bomb hits.
The commanders in the U.S. 5th Fleet had 956 carrier-based planes available to them. In addition, Ozawa’a pilots only had about 25 percent of the training and experience the American pilots had, and he was working with inferior equipment. His ships had antiaircraft guns, for example, but lacked the new proximity fuses, which provided a more sophisticated triggering mechanism than the common contact fuses or timed fuses did, as well as good radar.
The Japanese fleet rendezvoused June 16 in the western part of the Philippine Sea. Japanese aircraft did have a superior range at that time, though, which allowed them to engage the American carriers beyond the range of American aircraft. They could attack at 300 miles and could search a radius of 560 miles, while the American Hellcat fighters were limited to an attack range of 200 miles and a search range of 325 miles. Additionally, with their island bases in the area, the Japanese believed their aircraft could attack the U.S. fleet and then land on the island airfields. They could thus shuttle between the islands and the attack, and the U.S. fleet would be receiving punishment with only a limited ability to respond.
A Major Battle on the Horizon…
The American air raids on the Marianas continued through June 15, and U.S. ships began an additional bombardment of the islands. On June 15, three divisions of American troops, two Marine divisions and one Army division, went ashore on Saipan, and Toyoda committed nearly the entire Japanese Navy to a counterattack. Toyoda wired Ozawa that he was to attack the Americans and annihilate their fleet. “The rise and fall of Imperial Japan depends on this one battle,” Toyoda wrote.