The Battle of Leyte Gulf (23–26 October 1944) was the largest naval battle of World War II and by some criteria the largest naval battle in history, with over 200,000 naval personnel involved.
By late 1944, the Japanese fleet had become much weaker than that of the Allied forces; it contained fewer capital ships (aircraft carriers and battleships) than the Allies had aircraft carriers in the Pacific. After the catastrophic Battle of the Philippine Sea in June 1944, senior Japanese military leaders understood that their remaining naval forces were incapable of achieving a strategic victory against the Allies. However, the Japanese general staff believed that continuing to contest Allied offensives at sea was necessary to deter an invasion of mainland Japan and to give the Japanese navy an opportunity to use its remaining strength. As a result, the Imperial Japanese Navy (IJN) mobilized nearly all of its remaining major naval vessels in an attempt to repel the Allied invasion of the Philippines, but it was defeated by the U.S. Navy's Third and Seventh Fleets.
The battle consisted of four main engagements (the Battle of the Sibuyan Sea, the Battle of Surigao Strait, the Battle off Cape Engaño, and the Battle off Samar) and several lesser actions. Allied forces announced the end of organized Japanese resistance on the island of Leyte at the end of December.
It was the first battle in which Japanese aircraft carried out organized kamikaze attacks, and it was the last-ever battle between battleships. The Japanese navy suffered crippling losses and did not sail in comparable force for the remainder of the war, as most of its vessels were stranded in port for lack of fuel.
The Allied campaigns of August 1942 to early 1944 had pushed Japanese forces from many of their island bases in the south and central Pacific Ocean, while isolating many of their other bases (most notably in the Solomon Islands, Bismarck Archipelago, Admiralty Islands, New Guinea, Marshall Islands, and Wake Island). In June 1944 a series of American amphibious landings supported by the U.S. Fifth Fleet's Fast Carrier Task Force captured most of the Mariana Islands (but bypassing Rota). This offensive breached Japan's strategic inner defense perimeter and provided the Americans a base from which long-range Boeing B-29 Superfortress bombers could attack the Japanese home islands.
The Japanese attempted to interdict American landings in the Marianas during the Battle of the Philippine Sea in July 1944. In the course of the battle, the U.S. Navy destroyed three Japanese aircraft carriers, damaged various other IJN ships, and shot down approximately 600 Japanese aircraft. This left the Japanese Navy with little carrier-borne air power and few experienced pilots. However, the considerable land-based air power that the Japanese had amassed in the Philippines was considered too dangerous to bypass by many high-ranking officers outside the Joint Chiefs of Staff, including Admiral Chester Nimitz.
Formosa vs. Philippines as invasion target
The next logical step was to cut Japan's supply lines to Southeast Asia, depriving the Japanese empire of fuel and other critical supplies. However, there were two different plans for doing so. Admiral Ernest J. King, other members of the Joint Chiefs of Staff, and Admiral Nimitz favored blockading Japanese forces in the Philippines and invading Formosa (Taiwan), while U.S. Army General Douglas MacArthur, wishing to fulfill his 1942 promise to "return" to the Philippines, championed an invasion of the islands.
While Formosa could also serve as a base for an invasion of mainland China, which MacArthur felt was unnecessary, it was also estimated that an invasion of the island would require about 12 divisions from the Army and Marines. Meanwhile, the Australian Army, spread thin by engagements in the Solomon Islands, New Guinea, the Dutch East Indies and various other Pacific islands, would not have been able to spare any troops for such an operation. As a result, an invasion of Formosa, or any operation requiring much larger ground forces than were available in the Pacific in late 1944, would be delayed until the defeat of Germany made the necessary manpower available.
Decision to invade the Philippines
A meeting between MacArthur, Nimitz, and President Roosevelt helped confirm the Philippines as a strategic target but did not reach a decision, and the debate continued for two months. Eventually Nimitz changed his mind and agreed to MacArthur's plan, and it was eventually decided that MacArthur's forces would invade the island of Leyte in the central Philippines. Amphibious forces and close naval support would be provided by Seventh Fleet, commanded by Vice Admiral Thomas C. Kinkaid.
By late 1944, the U.S. Seventh Fleet contained units of the U.S. Navy and the Royal Australian Navy. Before the major naval actions in Leyte Gulf had begun, HMAS Australia and USS Honolulu were severely damaged by Japanese air attacks; during the battle proper these two cruisers were retiring, escorted by HMAS Warramunga, for repairs at the major Allied base at Manus Island, 1,700 mi (2,700 km) away.
Lack of unified command structures
American strategists decided that the U.S. Third Fleet, commanded by Admiral William F. Halsey Jr., with Task Force 38 (TF 38, the Fast Carrier Task Force, commanded by Vice Admiral Marc Mitscher) as its main component, would provide more distant air cover for the invasion. A fundamental defect in this plan was there would be no single American admiral in overall command. Kinkaid fell under MacArthur as Supreme Allied Commander Southwest Pacific Area, whereas Halsey's Third Fleet reported to Nimitz as Commander-in-Chief Pacific Ocean Areas. This lack of unity of command, along with failures in communication, nearly resulted in a strategic disaster for the American forces during the battle. Coincidentally, the Japanese plan also lacked an overall commander, and IJN forces were split into three separate fleets.
Following the Battle of the Philippine Sea, the next possible axes of Allied attacks were readily apparent to the IJN. Combined Fleet Chief Soemu Toyoda prepared four "victory" plans: Shō-Gō 1 (捷1号作戦, Shō ichigō sakusen) envisioned attacking American forces attempting to invade the Philippines, while Shō-Gō 2, Shō-Gō 3 and Shō-Gō 4 were conceived as potential responses to American attacks on Formosa, the Ryukyu Islands, and the Kurile Islands respectively. The plans called for complex offensive operations, and involved committing nearly all available forces to a decisive naval battle, despite substantially depleting Japan's diminishing reserves of fuel oil.
On 12 October 1944, Halsey began a series of carrier raids against Formosa and the Ryukyu Islands with the goal of ensuring that Japanese aircraft based there could not interdict the American amphibious landings on Leyte. The Japanese command, therefore, put Shō-Gō 2 into action, launching waves of air attacks against the Third Fleet's carriers. In what Admiral Halsey refers to as a "knock-down, drag-out fight between carrier-based and land-based air", the Japanese were routed, losing roughly 600 aircraft in three days – almost their entire air strength in the region. Following the American invasion of the Philippines, the Japanese Navy made the transition to Shō-Gō 1.
Shō-Gō 1 called for Vice Admiral Jisaburō Ozawa's ships—known as the "Northern Force"—to lure the American Fast Carrier Task Force away from Leyte. The Northern Force would be built around several IJN aircraft carriers, but these carriers would be equipped with very few aircraft or trained aircrew. Instead, their role was to serve as a distraction. As the U.S. covering forces were lured away by Ozawa's carriers, two other IJN surface fleets would advance on Leyte from the west. The "Southern Force" under Vice Admirals Shoji Nishimura and Kiyohide Shima would strike at the landing area via the Surigao Strait. The "Center Force" under Vice Admiral Takeo Kurita—by far the most powerful of the attacking Japanese forces—would pass through the San Bernardino Strait into the Philippine Sea, turn southwards, and then also attack the landing area.