He enlisted in August 1940 and a year later he was assigned to Canadian Military Headquarters in London. As an official war artist, which he was in effect from February 1942 to September 1946, he painted a number of scenes in the United Kingdom, including anti-aircraft defences on the Thames estuary, Forestry Corps camps, and invasion training in Scotland. In Sicily and Italy he followed the units of the First Canadian Infantry Division. In North-West Europe, he depicted the activities of the men of the Fourth Canadian Armoured Division and the airborne operations that were part of the Normandy invasion.

At the end of hostilities, he obtained a position as a professor at the Ontario College of Art in Toronto. He travelled to South Africa and Greece. He was awarded a government fellowship to paint in Italy.