[3] They are usually high-ranking members of the armed forces who retain their commission while being accorded full diplomatic status and immunity.The term "attaché" is French and denotes an individual who is assigned ("attached") to a diplomatic mission to fulfill a particular specialized function.As a formal diplomatic practice, the defence attaché system is traced to the Thirty Years' War (1618–1648), when French Foreign Secretary Armand Jean du Plessis, First Duke of Richelieu dispatched military officers abroad to liaise with allied powers, monitor military developments and gather intelligence.A series of military officers had been assigned to the American diplomatic mission in Tokyo since 1901, when the U.S. and Japan were co-operating closely in response to the Boxer Rebellion of 1899–1901 in China.These "language officers" translated training and technical manuals and reported on conditions in Japanese military units.