The Vietnamese Rangers (Vietnamese: Biệt Động Quân), commonly known as the ARVN Rangers, 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.