The Vietnam War was a dark time of brutal guerrilla warfare in dense jungles, shady covert operations that make you question humanity, and a protest movement that shook the country. The CIA was everywhere in South Vietnam, gathering intel on the Ho Chi Minh trail and planting mercenaries to disrupt the supply lines. What they did when they ran out of men was pretty despicable.
The CIA started recruiting mercenaries from among the native Hmong hill tribes to stop supplies from reaching the Vietcong and stop the infiltration of Laos and norther Thailand. War with Laos and Cambodia wasn't an option, so America's involvement had to be kept secret, so everything was managed through the CIA-owned airline Air America.
Planes would drop rice on villages that offered warriors to fight their secret war. Once involved, there was no backing out. Quitting meant they were treated as an enemy or denounced. When more soldiers died off or abandoned America's secret war, children were put in their place to fill the numbers. At the peak of fighting in 1971, about 40% of the soldiers were Hmong, and most were child soldiers, no more than 13 or 14 years old.