Japanese naval aviation predated the Sempill Mission: Japan had conducted naval air attacks at Tsingtao and was already developing the purpose-built carrier Hosho. The mission gave Japan access to extensive British scientific and technical knowledge at a crucial stage. British personnel could also inspect Japanese facilities and assess the country's aviation capabilities. The mission therefore combined assistance with observation, much as Captain William Pakenham and other British observers had done at Tsushima. Japanese use of British-built ships there had supplied evidence about modern pre-dreadnought performance against a Russian fleet shaped by French technology. In both cases, cooperation gave Britain an unusually close view of what its partner could do.
Chapter · 32:41-36:55
The Sempill Mission transferred knowledge and assessed Japan
Britain shared advanced naval-aviation expertise with a Japan already developing Hosho while using the mission to inspect Japanese facilities as the alliance weakened.