The Civilian Irregular Defense Group was a military program developed by the Central Intelligence Agency (CIA) during the Vietnam War, which was intended to develop South Vietnamese irregular military units from indigenous ethnic-minority populations. The main purpose of setting up the CIDG program was to counter the growing influence of Viet Cong (VC) in the Central Highlands by training and arming the villagers for village defense. The program rapidly expanded after the US military transferred its control from CIA to MACV after two years since its inception and changed its focus from village defense to more conventional operations. From June 1967 onwards the CIDG members were made part of the Army of the Republic of Vietnam (ARVN) or other government agencies to increase Vietnamese participation. By late 1970, the remaining CIDG camps were converted to Vietnamese Rangers camps. The indigenous ethnic-minority people that formed the CIDG reaped significant benefits by the government of South Vietnam for their allegiance and it was the first time that minority groups were given full status as citizens of South Vietnam.

The Vietnamese Rangers (Vietnamese: Biệt Động Quân), commonly known as the ARVN Rangers or Vietnamese Ranger Corp (VNRC), were the light infantry of the Army of the Republic of Vietnam. Trained and assisted by American Special Forces and Ranger advisers, the Vietnamese Rangers infiltrated beyond enemy lines in search and destroy missions. Initially trained as a counter-insurgency light infantry force by removing the fourth company each of the existing infantry battalions, they later expanded into a swing force capable of conventional as well as counter-insurgency operations, and were relied on to retake captured regions. Later during Vietnamization the Civilian Irregular Defense Group program was transferred from MACV and integrated as Border Battalions responsible for manning remote outposts in the Central Highlands.