After the war he returned to the United Kingdom on the SS "Orotava" which arrived at Southampton in early September 1902, only to depart again in 1903 on a special mission to Japan as British military attache at the Japanese headquarters during the Russo-Japanese War. While there, he observed the use by the Japanese of a tethered balloon at Port Arthur. At the start of 1908, Bannerman was sent to the War Office to work as a general staff officer (third class).