Sempill Mission

The Sempill Mission was a British aeronaval technical mission led by Captain the Master of Sempill and sent to Japan in September 1921, with the objective of helping the Imperial Japanese Navy develop its aeronaval forces. The mission consisted in a group of 30 instructors and support staff, headed by Colonel Sempill, and stayed in Japan for 18 months.

The Mission started training operation at the air base of Kasumigaura. The Japanese were trained on several new aircraft, such as the Gloster Sparrowhawk, in various techniques such as torpedo bombing and flight control.

The Mission also brought the plans of the most recent British aircraft carriers, such as HMS Argus and HMS Hermes, which influenced the final stages of the development of the Japanese aircraft carrier Hōshō. Although the Hōshō was already launched by that time, she became the first aircraft carrier laid down as such in the world when she was commissioned in 1922, one year before the Hermes.