The Hmong hill tribe in Laos was recruited in 1961 by the CIA, to fight a "Secret War" against the Communists of North Vietnam. Their job was to try to block the Vietcong's supply route.
Known as the "Ho Chi Minh trail", it ran through Laos, along the border with Vietnam. More than 40,000 Hmong were killed in the fighting that followed.
When the US fled Saigon in 1975, Communists also seized control of Laos.
The Hmong, abandoned by the US, allegedly became the target of retaliation and persecution.
This marked the beginning of the mass exodus of Hmong refugees into Thailand, which eventually swelled to more than 300,000.
Hmong fighters in the jungles of Laos
Some of them were eventually resettled in the US, but many continue to languish in Thai detention camps. And at least 7,000 Hmong are still hiding in the mountains and jungles of Laos, including some former CIA fighters.