With their victory in the Russo-Japanese War of 1904–05, the Japanese became concerned about the potential for conflict with the USA. The theorist Satō Tetsutarō developed the doctrine that Japan should have a battlefleet at least 70% the size of that of the U.S. This would enable the Japanese navy to win two decisive battles, the first early in a war against the U.S. Pacific Fleet, and the second against the U.S. Atlantic Fleet which would inevitably be dispatched as reinforcements.
Japan’s first priorities were to refit the pre-dreadnoughts she had captured from Russia and to complete Satsuma and Aki. The Satsumas were designed before Dreadnought, but financial shortages resulting from the Russo-Japanese War delayed her completion and resulted in her carrying a mixed armament, so she was known as a ‘semi-dreadnought’. These were followed by a modified Aki-type: Kawachi and Settsu. These two ships were laid down in 1909 and completed in 1912. They were armed with twelve 12-inch (305 mm) guns, but they were of two different models with differing barrel lengths, meaning that they would have had difficulty controlling their fire at long ranges.