Giambastiani also led Submarine Development Squadron Twelve, an operational submarine squadron that also serves as the Navy's Warfare Center of Excellence for submarine doctrine and tactics. Established in 1949, Submarine Development Squadron Twelve is the oldest experimental unit of its kind in the U.S. military. He served as the first director of strategy and concepts at the Naval Doctrine Command, as well as Commander, Atlantic Fleet Submarine Force; Commander, Submarines Allied Command Atlantic; and Commander, Anti-Submarine and Reconnaissance Forces Atlantic in Norfolk, Virginia.