The early history of the Hmong has proven difficult to trace, but theories that place the origin of the Hmong/Mong people in Mesopotamia, Siberia, or Mongolia have been disputed by recent studies. According to Ratliff, there is linguistic evidence to suggest that they have occupied the same areas of southern China for at least the past 2,000 years. Evidence from mitochondrial DNA in Hmong-Mien/Miao-Yao language speaking populations supports the southern origins of maternal lineages even further back in time, although Hmong/Miao speaking populations show more contact with northeast Asians (i.e. northern Han) than Mien/Yao populations. Historical Chinese documents describe that area being inhabited by 'Miao' people, a group with whom Hmong people are often identified.

In the early 1960s, the U.S. Central Intelligence Agency (CIA) began to recruit the indigenous Hmong people in Laos to join fighting the Vietnam War, named as a Special Guerrilla Unit led by General Vang Pao. About 60% of the Hmong men in Laos were recruited by the CIA to join fighting for the "Secret War" in Laos. The CIA used the Special Guerrilla Unit as the counter attack unit to block the Ho Chi Minh Trail, the main military supply route from the north to the south. Hmong soldiers put their lives at risk in the frontline fighting for the United States to block the supply line and to rescue downed American pilots. As a result, the Hmong suffered a very high casualty rate; more than 40,000 Hmong were killed in the frontline, countless men were missing in action, thousands more were injured and disabled.