When the war began in June 1812, the 41st were stationed in Upper Canada. Procter was sent to Amherstburg near the westernmost part of the province, to relieve the commandant of Fort Malden and defend the fort against a possible American assault. He fought several skirmishes, which helped isolate the American post at Fort Detroit and contributed to its capture by General Brock. When Brock departed, Procter was left in command on the Detroit frontier. He was soon faced with an attack by American General William Henry Harrison, who intended to expel the British from Michigan.