 The 3d Marine Division began operating in Vietnam when on March 6 , 1965 , they opened a Marine Compound at the Da Nang Air Base . On July 4 , 1965 , 2nd Battalion , 9th Marines were ordered to Vietnam from Okinawa . 2nd Battalion , 9th Marines fought battles in or around Danang , Hue , Phu Bai , Đông Hà , Camp Carroll , Cam Lộ , Con Thien , Than Cam Son , Quảng Trị , Cửa Việt , Vandegrift Combat Base and what is considered by many as their most vicious engagement , the Battle of Khe Sanh . 
