Drastically Modified Combined Fleet

Chapter 5 - Washington Naval Treaty

The conferences between various countries at the Washington Naval Treaty held in 1921 were tumultuous, but despite the noisy discussions, there was some progress in reaching an agreement, particularly regarding the ownership of battleships. The United States and Britain already had agreements for 500.000 tons each, while Japan had 250.000 tons, and France and Italy had 175.000 tons each. However, a separate dispute arose between Japan and the United States and Britain regarding the completion status of the second ship of the Nagato-class battleship, the Mutsu.

According to the treaty, unfinished ships were supposed to be scrapped, but Japan claimed that the Mutsu had already been completed, while the US and Britain argued that it was still unfinished. For the US and Britain, the Nagato-class battleship posed a threat like no other. Equipped with the largest caliber 40 cm guns (actually 41 centimeters), and with a publicly stated speed of 23 knots, it was inconceivable to take these figures at face value given the inferred engine capacity from the ship's design. In fact, some Western experts estimated the speed of the Nagato to be over 26 knots. Moreover, if it carried 40 cm guns, its defense capabilities would likely correspondingly be formidable. In terms of overall performance considering firepower, defense, and speed, there was no battleship in the US and Britain that could compete with the Nagato-class at that time. Especially for the United States facing Japan across the Pacific, the addition of such a powerful ship would significantly increase its military burden without a doubt.

Nevertheless, all countries maintained their policy to prioritize the signing of the treaty. In the end, through negotiations between the parties, Japan was allowed to retain the Mutsu, and in return, the US was permitted to construct two 40 cm gun-equipped battleships named West Virginia and Colorado. Britain was also allowed to build two new battleships equipped with 40 cm guns.

The background to Japan being allowed to keep the Mutsu was influenced by the fact that Britain, having lost two Kongō-class battlecruisers lent by Japan during World War I, felt indebted to Japan. Additionally, for Britain, Japan's military expansion served as a check against the United States, making it not entirely unfavorable. Of course, if Japan were to pose a threat to British colonies, it would be a different story, but at that time, the likelihood of such an event seemed relatively low.

In any case, once this conference concludes, Japan will be able to possess a total of eight battleships: the Nagato and Mutsu equipped with 40 cm guns, the Ise, Hyūga, Yamashiro, and Fusō with 36 cm guns. Although the main battleships preceding the Kawachi-class will all be scrapped, they are considered outdated vessels such as the pre- and semi-dreadnoughts, so their loss was not particularly regrettable.

Concerning the eight permitted battleships, the actual displacement was just under half of that of the United States and Britain. Nevertheless, considering the ratio of battleships equipped with 40 cm guns, it can be said that Japan received favorable treatment, making it a satisfactory outcome for the Imperial Japanese Navy. Within the Imperial Navy, there were voices advocating that not just half but 70% of the main battleships were necessary. However, based on the experiences of the Russo-Japanese War and World War I, those who believed that large battleships and big guns were suitable for Japan's military were already a minority.

The victory of the Imperial Navy in the Battle of Tsushima during the Russo-Japanese War was attributed not to the excellence of fleet movements or gunnery skills but rather to the extreme fatigue of the Russian side, along with the effective use of wireless communication in Japan's fleet—a victory achieved through the utilization of information networks on the battlefield, a common understanding among Imperial Navy officers.

In the subsequent World War I, it was the U-boat fleet, not Germany's battleship fleet, that cornered the naval power of the maritime empire, Britain—a fact confirmed by history and echoed in research within the Imperial Navy. Therefore, Japan, which lagged behind in technological advancements compared to the West, needed substantial research and development funds to bridge this gap. Moreover, preparation against new threats capable of three-dimensional mobility, such as airplanes and submarines, was imperative. The lessons learned from the Russo-Japanese War, emphasizing hygiene, healthcare, and the importance of information and communication, combined with the difficulties in anti-submarine warfare and convoy escort highlighted in World War I, called for the establishment of various schools and training facilities, as well as urgent reinforcement of escort vessels and aviation units.

However, being a financially constrained navy, the Imperial Navy could not afford to lavish funds solely on battleships. Therefore, despite being mocked as a "Fifty Percent Navy," the top brass of the Imperial Japanese Navy accepted this result.