A small-scale ethnic insurgency began in Laos after the establishment of the Laotian People's Democratic Republic (LPDR) by the Pathet Lao in 1975. This insurgency never seriously threatened the regime, but it proved troublesome because the insurgents committed sabotage, blew up bridges, and threatened transport and communications. The great majority of insurgents were Hmong, led by ex-soldiers from United States Central Intelligence Agency (CIA) - supported units who fought against Pathet Lao and North Vietnamese troops in the 1960s. Hmong groups, most of them associated with the former Royal Laotian government, drew recruits and support from Hmong refugee camps in Thailand and operated primarily from bases in Thailand with the cooperation of local Thai military officers. The Hmong also gained support from China for their insurgency because of the presence of some 45,000 Vietnamese troops in Laos during this period -- which was vehemently opposed by the Chinese. ( In 1982, an anti-Pathet Lao "Royal Lao Democratic Government," backed by China, was set up in southern Laos.)
In the early 1980s, Hmong insurgents claimed that the Lao People's Army was using lethal chemical agents against them. The Hmong refugees in Thailand often referred to the chemical agents as "poisons from above;" foreign journalists used the term "yellow rain." The LPDR government vehemently denied these charges. The United States Department of State noted in 1992 that "considerable investigative efforts in recent years have revealed no evidence of chemical weapons use" in the post-1983 period.
In 1988, about half of the Vietnamese troops in Laos were withdrawn, and China ceased to support anti-Pathet Lao resistance. From their sanctuaries in Thailand, the Hmong continued their armed resistance efforts against the communists throughout the 1980s and into the 1990s. Many thousands of other Hmong, however, had sided with the Pathet Lao and were living peacefully in Laos, particularly in the northeastern provinces; others went to Thailand and then the United States.
Discussions between Laos and Thailand over guerrilla attacks led first to a suspension in hostilities in 1990 and then to the withdrawal of Thai troops from the border area in 1991. As relations between Thailand and Laos continued to improve in the 1990s, support for this insurgent activity declined. Resistance spokesmen claimed that their principal source of funds for weapons and supplies came from Laotian expatriate communities overseas, including the 180,000 Laotians in the United States.
As a result of decades of warfare, dislocation, and the military campaign mounted against them by Vietnamese and LPDR forces in the late 1970s and early 1980s, the Hmong population was reduced to approximately 200,000 in Laos and about the same number in Thailand in the early 1990s. By 1992, cross-border Hmong raids into Laos were reduced to little more than banditry -- a casualty of wavering Thai support and apathy among the Hmong themselves. Continued participation of Hmong in resistance activities posed no threat to the stability of the government of Laos, but it did complicate the repatriation process for the estimated 60,000 Laotian refugees in Thai camps.