emperor's aide-de-camp
Historical military officer who served as a personal aide to the Emperor of Japan, primarily during the Meiji through early Shōwa periods.
The aide-de-camp assisted the Emperor in military affairs as a close attendant.
侍従 is a broader term for a chamberlain or attendant to the Emperor, not necessarily a military officer, whereas 侍従武官 specifically denotes a military aide-de-camp.
Compound of 侍従 (chamberlain, attendant) and 武官 (military officer). The term was used in the Imperial Japanese military system.