The Battle of Leyte, which was supposed to be Japan's last stand, ended in defeat as their forces fell just short. As a result, Japan lost air and naval control around the Philippines, making transportation from the southern resource zone significantly challenging. Nevertheless, the Japanese military maintained a reasonable capacity for continued warfare.
About three years prior, in April 1942, responding to requests from Germany and the Imperial Army, the Combined Fleet advanced into the Indian Ocean and defeated the British Eastern Fleet defending the region, seizing control of the Indian Ocean. One of the reasons for the Combined Fleet's excursion into the Indian Ocean was a secret agreement with Hitler, the German leader, promising to provide the battleships Scharnhorst and Gneisenau if they could dominate the Indian Ocean.
Armed with nine 28 cm guns and boasting speed performance surpassing the Kongō-class battleships, the Scharnhorst and Gneisenau were highly coveted as a counterforce against rumored large American cruisers. However, inspired by the actions of the Japanese and Italian fleets, Hitler reneged on the promise to provide both ships. Furthermore, he demanded the handover of the captured armored carriers Indomitable and Formidable from the Battle of the Indian Ocean.
In exchange for accepting Hitler's audacious offer, the Imperial Navy demanded compensation. They requested various weapons, including aircraft, as well as industrial machinery, advanced technology, and a synthetic petroleum plant. Hitler readily agreed to this offer, sending not only the complete plant but also a considerable number of technicians to Japan. This improvement in Japan's capacity for continued warfare was advantageous for Hitler as Japan's efforts increased the flow of American war resources into the Pacific, thereby relieving pressure on the European front. Indeed, a significant portion of the US Navy's forces were deployed on the Pacific side, thanks to the actions of the Japanese Navy. From Germany's point of view, the Atlantic Fleet's strength was clearly declining, no doubt due to the success of the Japanese Navy.
On the other hand, during this period, the Imperial Navy feared above all else the possibility of an American naval blockade. In a fleet battle, there was no concern with the presence of the Yamato-class battleships. However, if the Americans avoided direct confrontations with the Yamato-class and instead launched a campaign of disruption using numerous submarines and aircraft, the Imperial Navy's imbalanced preparation centered around massive battleships would be at a disadvantage.
Synthetic oil served as insurance for Japan in case of a naval blockade. Without oil, even the most advanced ships and aircraft would become mere metal masses, and, most importantly, the production of essential supplies would become impossible. This insurance became a lifeline not only for the Imperial Navy but also for the Imperial Army and the Japanese population. The Imperial Navy established plants not only within the country but also on the continent, maintaining production levels close to planned targets. Additionally, synthetic oil played a role as a form of currency, with the Imperial Navy providing oil to the Imperial Army in exchange for various supplies, including the Type 100 reconnaissance plane (Ki-46).
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As the clash between the Combined Fleet and the US Fleet loomed, just before the confrontation, there were the figures of 54 Ki-46s, intermingled with numerous fighter planes, at Kanoya Base. All of them were Imperial Navy aircraft, provided by the Imperial Army. Among them, six planes were Ki-46-V, with engines replaced from Kinsei to Homare. Equipped with two 2.000-horsepower engines, the aircraft, when in perfect condition, could achieve a top speed of 660 kilometers per hour.
The other 48 planes were also equipped with Homare and classified as a new variant, but they were not reconnaissance planes; they were classified as special attack planes and referred to as "Ohka" among insiders. Normally, the Ki-46 is operated by a pilot and a reconnaissance crew member, but Ohka has only a pilot, and instead of a reconnaissance crew member in the rear seat, there were explosives. These pilots were skilled land-based and carrier-based bomber pilots, a rare commodity in the Imperial Navy who were supposed to sortie as soon as information about the enemy fleet's position was received.
The six Ki-46s were responsible for guidance and confirming results, and the Ohkas would not return once it engaged the enemy unless it failed to make contact. The Imperial Navy was determined to replicate the ruthless tactics that succeeded in the Battle of Leyte, this time using the Ohka.