The Marines also played an important role in the Vietnam War at battles such as Da Nang, Huế, and Khe Sanh. The Marines operated in the northern I Corps regions of South Vietnam and fought both a constant guerilla war against the Viet Cong and an off and on conventional war against North Vietnamese Army regulars. Marines also conducted the less well-known Combined Action Program that implemented unconventional techniques for counterinsurgency warfare. The Marine presence was withdrawn in 1971, but returned briefly in 1975 to evacuate Saigon and attempt to rescue the crew of the Mayagüez. 13,091 Marines were killed and 88,594 wounded during the war. As a footnote, the Marines in Vietnam suffered more casualties than both WWI and WWII combined, and 58 were awarded the Medal of Honor.