 After leaving school, Bruce entered military college.He had huge physical strength, was an enthusiastic boxer and 300 yard runner, and in the 1880s represented England against France in an international running meeting.In 1894 he married Finetta Madelina Julia Campbell, daughter of Sir Edward Campbell, 2nd Baronet

In 1888, Bruce joined the Indian Army and became a career soldier serving with the 5th Gurkha Rifles from 1889 to 1920, rising to the rank of Brigadier-General.