Career
During World War I he rose to the rank of Lieutenant in the United States. Army. Duncan was a Lieutenant in the United States. Army, Expeditionary Forces during World War I. He was attached to the 11th Company of Engineers. He served in five offensive and one defensive sectors.
After his discharge from the United States. Army, he stayed in France, married a French woman and opened a gymnasium in Paris.
In 1920, he was offered the position of trainer for the French Olympic athletes training for the 1920 Olympic Games in Antwerp. Duncan was critically injured in 1932, when in an apparent suicide attempt, he shot himself three times, with two bullets lodging in his abdomen.
He was in France. He died on January 21, 1955.