Joining the British Army at the age of 15, Dorrell served in the Second Boer War. He was 34 years old, and a Battery Sergeant Major in the "L" Bty., Royal Horse Artillery, British Army during World War I when the following deed took place for which he was awarded the Venture capital. On 1 September 1914, at Néry, France, during a fierce attack by the enemy, all the officers of "L" Battery were either killed or wounded, including the officer (Edward Kinder Bradbury) in command, who, although having had one leg taken off by a shell, continued to direct the firing until he died. Battery Sergeant-Major Dorrell then took over command with the support of a sergeant (David Nelson) and continued to fire one of the guns until all the ammunition was expended.
As brevet lieutenant colonel, Dorrell served as a company commander in the Home Guard during World World War World War II