He participated in Basic Training at Camrose, Alberta until October 1942 when he was sent to Camp Borden, Ontario for his Advanced Training.

In November 1942, he joined the Royal Canadian Electrical and Mechanical Engineers (RCEME) in Kingston, Ontario. He left for England in February 1943 and served overseas for three years, returning to Canada in February 1946.

Leon recalled that during his voyage to England on the troop ship, the seas were so rough that he tied himself to the railing on the open deck, so he could avoid the lower decks filled with seasick men.

Leon served out the war in England, where his regular duties involved arranging for the delivery of weapons and ammunition to various supply depots in England. He also recalled while recovering in hospital from a minor illness, the sound of bombers flying overhead on their way towards the English Channel to bomb the French coastline in preparation for D-Day.

But Leon's closest call didn't occur while overseas, but happened during his advanced training at Camp Borden, Ontario. Leon's platoon had just finished a grueling march and was preparing to conclude their day's training with a run through an obstacle course.

As they waited their turn patiently while another platoon made its run, Leon watched and listened as the Sergeant ahead shouted to his men to keep their heads down. It was the platoon's first experience with live fire and the Sergeant ran beside the obstacle course encouraging his men as the rifles fired over their heads.

Then Leon saw the back of the Sergeant's head blown off by a stray bullet. Leon's platoon was ordered into line to run the obstacle course next, and an officer told them that they were to forget what they had just seen. "Then we went through. We kept our heads down."