Gambiez was born in Lille, graduated from Saint Cyr in 1925. He served with the Foreign Legion in Morocco before studying at the Superior War School in 1935. He was a captain in command of a company during the Battle of France. He trained and commanded a Choc battalion in 1943, taking part in the fighting to liberate Corsica in 1944. Gambiez served as chief of staff to the French commander-in-chief Henri Navarre during the First Indochina War, including the Battle of Dien Bien Phu where one of his sons died.