Bainbridge joined the Royal East Kent Regiment (The Buffs) in 1888 and took part in the Dongola expedition in 1896 and the Nile expedition of 1897 and fought at the Battle of Omdurman in 1898. He commanded the 7th Mounted Infantry during the Second Boer War and took part in the Battle of Paardeberg in 1900. In 1903 he took command of the School of Mounted Infantry at Kilworth. He fought in the European War, from April 1915, as Commander of 110th (Leicester) Infantry Brigade and, from June 1916, as General Officer Commanding 25th Division. The Division went on to fight at the Battle of the Somme, at the Battle of Messines, at the Battle of Passchendaele, in the German offensive of March/April 1918 and at the Battle of Aisne under his leadership. After the War he became General Officer Commanding 1st Infantry Division before retiring in 1923.