In practice, it was a general term for the independent armed groups of the Khmer Rouge, which were primarily divided into three factions: In the years that followed, widespread dissatisfaction with the Sihanouk regime drove many Cambodians to flee government repression and join Khmer Rouge armed groups, leading to a rapid increase in the Revolutionary Army of Cambodia's ranks.

From 1972 onward, after Richard Nixon's visit to China, Pol Pot's faction received increased backing from Beijing and gradually consolidated absolute control over the Communist Party of Kampuchea (CPK).

Additionally, they conducted large-scale internal purges, not only removing remnants of Sihanouk's supporters but also eradicating any suspected dissent to centralise power further.

From as early as 1975, the Khmer Rouge launched cross-border attacks into Vietnam, burning villages, looting, and massacring civilians.

However, as Pol Pot prepared for a full-scale war against Vietnam, he initiated another purge, executing numerous Khmer Rouge officials suspected of Vietnamese ties.

By late 1978, Vietnam had established the Kampuchean United Front for National Salvation (FUNSK), composed of former Khmer Rouge officials, soldiers, and Cambodian exiles.

In just two weeks, Vietnamese forces obliterated the Khmer Rouge's main military divisions, captured Phnom Penh, and established the People's Republic of Kampuchea.

Despite this, the weaknesses of the People's Republic of Kampuchea (PRK) led to its complete dependence on Vietnam—a country that had just emerged from two major wars, was now engaged in two border conflicts, and was struggling with a devastated economy.

China, the United States, and ASEAN nations backed the formation of a Cambodian government-in-exile and the military alliance known as the Coalition Government of Democratic Kampuchea (CGDK), which included the Khmer Rouge, the Khmer People's National Liberation Front (KPNLF), and the royalist ANS (Armee Nationale Sihanoukiste).

However, the Khmer Rouge remained the dominant military force within this three-party coalition, playing the leading role in prolonging the conflict against the Vietnam-backed Phnom Penh government for a decade.

During this period, the Khmer Rouge continued to receive foreign support from China, the United States, Thailand, and other countries hostile to Vietnam.