In early 1915 McKean enlisted in the
Canadian Expeditionary Force. He was awarded three separate medals for outstanding valour. In the course of his military service, he received the Military Medal and the Victoria Cross and, after he was commissioned as an officer, the Military Cross. He was one of only a handful of people who have won all three and lived to peacetime. As a corporal in 1917, he was awarded the Military Medal for rescuing wounded men under fire. A year later, he was 29 years old, and a
lieutenant in the 14th (
The Royal Montreal Regiment) Battalion, when the following deed took place for which he was awarded the Victoria Cross. On 27/28 April 1918 at the
Gavrelle Sector,
France, when Lieutenant McKean's party was held up at a block in the communication trench by intense fire, he ran into the open, leaping over the block head first on top of one of the enemy. Whilst lying there, he was attacked by another with a fixed bayonet. He shot both of these men, captured the position, then sent back for more bombs, and until they arrived he engaged the enemy single-handed. He then rushed a second block, killing two of the enemy, capturing four others, and driving the remainder into a dug-out, which he then destroyed. He later achieved the rank of
captain. In the closing months of the war,
Canada's Hundred Days, he led the capture of Cagnicourt near Arras, using, one historian wrote, "little but courage and bravado." He won the Military Cross but was probably due another Victoria Cross as his actions were so incredible. McKean wrote of his wartime experiences in
Scouting Thrills: The Memoir of a Scout Officer in the Great War (1919, re-issued by CEF Books in 2003). He remained with the army after the end of World War I, serving in Egypt. He left the army in March 1926. ==Later life==