In 1921, during the Interwar period, Japan developed and launched the , which was the first purpose-designed aircraft carrier in the world."The Imperial Japanese Navy was a pioneer in naval aviation, having commissioned the world's first built-from-the-keel-up carrier, the Hōshō.". pre-dated Hōshō and had a long landing deck, but was designed and initially built as an ocean liner. The first purpose-designed aircraft carrier to be laid down was in 1918 but she was completed after Hōshō. Japan subsequently developed a fleet of aircraft carriers that was second to none.
