A powerful, square-jawed, silver-haired character actor with a deep, distinctive crease across the bridge of his nose, Duke debuted onscreen in Patterns (1956), going on to a busy screen and TV career in which he often played resolute types and dignified military officers. He starred in the TV miniseries The Winds of War and in four TV series: Bourbon Street, Lancer, Room for One More, and Twelve O'Clock High.