Cooper graduated from Stanford University with a bachelor's degree in political science. He received a regular commission in the United States Marine Corps (USMC) in September 1941. During World War II he served in the Pacific theatre on the USS Pennsylvania. By the end of the war he had been promoted to major. He resigned his commission in 1949, but returned to active duty during the Korean War, where he was involved in irregular warfare, and was promoted to lieutenant colonel. After the Korean War, the Marine Corps declined his application to remain on active duty. In the mid-1960s, he received a master's degree in history from the University of California, Riverside. From the late 1950s through the early 1970s, he was a part-time high school and community college history teacher.[1]
