[1] During World War I, Thompson, at the age of 18 years, enlisted as Gunner[2] with the 10th (Halifax) Siege Battery,[3] 3rd Brigade, Canadian Garrison Artillery (CGA).
After graduating, he was posted as the Medical Officer (Non-Permanent Active Militia) of 4th Divisional Train, and the Royal Montreal Regiment.
He remained in the position until 1940; at which time he was posted to 6th Field Ambulance, a non-permanent militia until of the Royal Canadian Army Medical Corps (RCAMC).
[3] With the outbreak of World War II, Thompson was called to Active Service in 1941 with the rank of Lieutenant-Colonel, took command of No.
"[3] Following the end of the war, Thompson was promoted to Brigadier and appointed Director General (Army), in 1946.