The Republic of Vietnam Marine Division was part of the armed forces of South Vietnam. It was established by Ngo Dinh Diem in 1954 when he was Prime Minister of the State of Vietnam, which became the Republic of Vietnam in 1955. The longest-serving commander was Lieutenant General Le Nguyen Khang. In 1969, the VNMC had a strength of 9,300, 15,000 by 1973, and 20,000 by 1975.

Operation Coronado IX was a riverine military operation conducted by the Mobile Riverine Force (MRF) of the United States and elements of the Army of the Republic of Vietnam (ARVN) from November 1967 to January 1968 in an attempt to destroy Viet Cong (VC) strongholds in the Mekong Delta. In the middle of November, clashes resulted in the capture of VC supplies and hideouts. During this period, the VC lost 178 men but killed only 26. For the next few weeks there was little contact, although some abandoned VC bunkers were destroyed and supplies captured. On 4 December, a large engagement occurred when a VC battalion encountered the South Vietnamese 5th Marine Battalion. 266 VC were killed, mostly by the Marines. The Marines lost 40 killed, while the Americans suffered 9 dead. Over the next month and the Christmas period, there was only sporadic skirmishes, but at the start of the new year, there were some medium size battles in which the Americans killed a few dozen VC. After this there was little contact.