K5 Plan

The K5 Plan, K5 Belt or K5 Project, also known as Bamboo Curtain, was an attempt between 1985 and 1989 by the government of the People's Republic of Kampuchea to seal Khmer Rouge guerrilla infiltration routes into Cambodia by means of trenches, wire fences, and minefields along virtually the entire Thai–Cambodian border.

After the defeat of Democratic Kampuchea in 1979, the Khmer Rouge fled Cambodia quickly. Protected by the Thai state, and with powerful foreign connections, Pol Pot's virtually intact militia of about 30,000 to 35,000 troops regrouped and reorganized in forested and mountainous zones behind the Thai-Cambodian border. During the early 1980s Khmer Rouge forces showed their strength in Thailand, inside the refugee camps near the border, and were able to receive a steady and abundant supply of military equipment. The weapons came mainly from China and the US and were channeled across Thailand with the cooperation of the Royal Thai Armed Forces.

From their position of security in hidden military outposts along the Thai border, the Khmer Rouge militias launched a relentless military campaign against the newly established People's Republic of Kampuchea state. Even though the Khmer Rouge was dominant, it fought against the Kampuchean People's Revolutionary Armed Forces (KPRAF) and Vietnam People's Army along with minor non-communist armed factions which had formerly been fighting against the Khmer Rouge between 1975 and 1979.

The border war followed a wet season / dry season rhythm. Generally, the heavily armed Vietnamese forces conducted offensive operations during the dry seasons, and the Chinese-backed Khmer Rouge held the initiative during the rainy seasons. In 1982, Vietnam launched a largely unsuccessful offensive against the main Khmer Rouge base at Phnom Malai in the Cardamom Mountains.

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