Formosa Air Battle

The Formosa Air Battle (Japanese: 台湾沖航空戦, lit. 'Battle of the Taiwan Sea', Chinese: 臺灣空戰), 12–16 October 1944, was a series of large-scale aerial engagements between carrier air groups of the United States Navy Fast Carrier Task Force (TF 38) and Japanese land-based air forces of the Imperial Japanese Navy (IJN) and Imperial Japanese Army (IJA). The battle consisted of American air raids against Japanese military installations on Taiwan (then known to Westerners as Formosa) during the day and Japanese air attacks at night against American ships. Japanese losses exceeded 300 planes destroyed in the air, while American losses amounted to fewer than 100 aircraft destroyed and two cruisers damaged. This outcome effectively deprived the Japanese Navy's Combined Fleet of air cover for future operations, which proved decisive during the Battle of Leyte Gulf later in October.

Japanese strategic plans for a decisive battle with the U.S. fleet were already established by September 1944. Anticipating the various options open to American landing forces, the Japanese operational order, code named Sho ("victory"), envisioned four scenarios numbered from one to four. Sho-1 (Ichi), 2 (Ni), 3 (San), and 4 (Yon) were meant to defend respectively the Philippines, Formosa and Okinawa, the Japanese homeland, and Hokkaido plus the Kuril Islands.

Due to Japan's losses during the Battle of the Philippine Sea, the core of its air power for operation Sho was land-based. The plan also broke with IJN tradition by assigning overriding importance to sinking U.S. supply vessels rather than U.S. warships. To restore morale, the Commander-in-Chief of the Combined Fleet Admiral Soemu Toyoda flew out to the front in early October to rally the troops behind Sho.

The Japanese navy had formed a special air unit called the T Attack Force (T攻撃部隊, T Kōgeki Butai), the "T" short for "typhoon" (台風, taifū), to experiment with rough-weather training. This strategy, along with night operations and submarine warfare, was meant to compensate for Japan's smaller fleet compared to that of the United States by flying missions in weather conditions that the Americans were not trained for. However, like other Japanese units at the time, the T Attack Force suffered from a shortage of pilots, even after recruiting green fliers directly from the army. Their inexperience, compounded by carrying out missions at night, would later lead to poor performance and exaggerated kill counts during the actual battle.

By 10 October Toyoda's tour of the front was complete. He intended to depart from Formosa for Japan that same day but was forced to change his plans when Vice Admiral Marc Mitscher's Fast Carrier Task Force suddenly appeared to the north, launching strikes against the Ryukyu Islands. Toyoda could not risk a return trip home through a concentrated enemy carrier force that now embarked more than 1,000 aircraft, especially not after previous Combined Fleet commanders had been lost during aerial engagements. As a result, he was grounded far from Combined Fleet headquarters at a decisive moment. Out of position and with inadequate lines of communication, the response to such overwhelming enemy air power was left to Toyoda's Chief of Staff, Vice Admiral Ryūnosuke Kusaka.

Kusaka correctly saw these strikes as a precursor to U.S. troop landings, in part due to Imperial Navy intelligence collected over the previous week. Because he was still unsure exactly where enemy forces would land, he chose to execute the air component of Sho-1 or Sho-2 – the planned defense of the Philippines or Formosa, respectively – on the morning of 10 October. Sho was a complex plan involving multiple naval surface forces sortieing from bases as far away as Singapore and Japan. It would take these warships time to maneuver into position for a concerted attack. Rather than waiting for the arrival of the fleet for a combination of sea and air power, Kusaka ordered the air forces reserved for Sho to engage the enemy at once. He reinforced this order by implementing Sho-2 in full on the morning of 12 October.

Over 1,800 aircraft were allocated for Sho in total, but they were widely dispersed across the four operation regions. About one third of them were not battle-ready due to casualties and a lack of parts or trained pilots. When the fighting began, Vice Admiral Shigeru Fukudome had approximately 700 planes ready in Formosa and Kyushu. 100 or so aircraft in the Seto Inland Sea was later added to his command. Over the next four days, an additional 690 or so planes flew in from bases in Japan and China.

Although this represented a huge number of available aircraft, the Imperial Japanese Navy Air Service (IJNAS) was still recovering from losses suffered at the Battle of the Philippine Sea in June. While units were largely reconstituted in terms of quantity by this time, pilot quality was in clear decline. Moreover, though the overall number of planes committed to battle by 12 October dwarfed any force that Japan had previously fielded in the air, the U.S. Navy's Fast Carrier Force was capable of committing a much larger, significantly better-trained force.