Sully was born in 1927 or 1928 in France and fought against the Nazis in the French Resistance as a teenager and was wounded on his seventeenth birthday in Paris. After the liberation of Paris he enlisted in the French Army, fought the Nazis in Germany and then volunteered for the French Expeditionary Forces, arriving in Saigon when the Japanese surrendered in 1945. Discharged in Saigon, Sully tried his hand as a tea planter and rancher before turning to journalism. In 1947 he joined "Sud-Est Asiatique", a now defunct French magazine, working for them until 1953. He was assigned to cover the battle of Dien Bien Phu by Time-Life. He escaped from behind the Viet Minh lines. In 1959 he joined United Press International (UPI). He wrote articles for "Time" magazine and his photographs were carried by Black Star until he joined "Newsweek" in early 1961.