. In 1921, the Japanese government formally requested that the British dispatch a naval air mission, in order to develop and to provide a professional edge to Japanese naval aviation. There were reservations on the part of the Admiralty, about granting the Japanese unrestricted access to British technology. Despite this the British government sent an unofficial civil aviation mission to Japan. The Sempill Mission led by Captain William Forbes-Sempill, a former officer in the Royal Air Force experienced in the design and testing of Royal Navy aircraft during the First World War. The mission consisted of 27 members, who were largely personnel with experience in naval aviation and included pilots and engineers from several British aircraft manufacturing firms. The British technical mission left for Japan in September with the objective of helping the Imperial Japanese Navy develop and improve the proficiency of its naval air arm. The British government also hoped it would lead to a lucrative arms deal. The mission arrived at Kasumigaura Naval Air Station the following month, in November 1921, and stayed in Japan for 18 months. The Japanese were trained on several British aircraft such as the Gloster Sparrowhawk; as the mission also brought to Kasumigaura well over a hundred aircraft comprising twenty different models, five of which were then currently in service with the Royal Air Force, including the Sparrowhawk. These planes eventually provided the inspiration for the design of a number of Japanese naval aircraft. Technicians became familiar with the newest aerial weapons and equipment - torpedoes, bombs, machine guns, cameras, and communications gear. Naval aviators were trained in various techniques such as torpedo bombing, flight control and carrier landing and take-offs; skills that would later be employed in the shallow waters of Pearl Harbor in December 1941. 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 carrier Hōshō. By the time the last members of the mission had returned to Britain, the Japanese had acquired a reasonable grasp of the latest aviation technology and the Sempill mission of 1921–22 marked the true beginning of an effective Japanese naval air force. Japanese naval aviation also, both in technology and in doctrine, continued to be dependent on the British model for most of the 1920s. The military in Japan were also aided in their