Born in Georgetown, Ballantine enrolled at the Royal Military College in 1894 and was a member of the 20th Halton Battalion.

He received training at Aldershot and graduated in time to join the British Army for the Second Boer War.

[1] Ballantine remained in the military after the war and served in posts within Canada until the outbreak of World War I. Then-Major Ballantine initially served as second in command of the 4th Battalion but assumed temporary control after Arthur Birchall was killed at the Second Battle of Ypres.

Ballantine returned to France with the 4th Battalion and commanded troops on the RMS Empress of Britain until he was mustered out in April of 1917.

Shortly after his appointment, he was also named as superintendent of ground and buildings as well as taking over the head coaching duties for the school's lacrosse, rifle and soccer teams.