Baker was educated in Gloucester and in Ceylon, and in 1848 entered the Ceylon Rifles as an ensign. He soon transferred to the 12th Lancers, and saw active service with that regiment in the 8th Cape Frontier War of 1852–1853. In the Crimean War, Baker was present at the Battle of Chernaya River and at the fall of Sevastopol, and in 1859 he became major in the 10th Hussars, succeeding only a year later to the command. This position he held for 13 years, during which period the highest efficiency of his men was reached, and outside the regiment he did good service to his arm by his writings.