Ta Mok
After the downfall of the Khmer Republic in April 1975, the Khmers Rouge régime established the Revolutionary Army of Kampuchea (RAK). The army was composed of Khmer Rouge soldiers and defectors from Lon Nol's FANK. Defectors who joined the Khmer Rouge were never fully trusted by the original Khmer Rouge. They were later purged by Pol Pot, when thousands of Khmer Rouge soldiers and officers were ordered killed by the Khmer Rouge leadership. Like the other forces, the RAK was organised to the division level and commanded by Chiefs of the General Staff Son Sen and Ta Mok. The RAK's 375,000-person, fully armed force was supplied by China and several Eastern bloc countries. When Democratic Kampuchea invaded Kampuchea Krom in southern Vietnam (known as Prey Nokor when it was Cambodian territory before 1949), the Vietnamese forces were caught off-guard and their double agents in the Khmer Rouge proved valuable. The double agents were later learned to have become members of the Kampuchean People's Revolutionary Armed Forces (KPRAF), the armed forces of the People's Republic of Kampuchea.