How bad was the heroin problem during the Vietnam War?
In southeast Asia, the governments of most countries and many colonial officials had been involved in the opium trade for a very long time. The Vietnam War and CIA operations in Laos had the unintended consequence of first opening up many areas of Southeast Asia to modern transportation and then presenting a ready-made market for the drug among the U.S. military personnel stationed in the region.
The turning point came in 1970-71 when the first high-grade heroin laboratories opened in the Golden Triangle. Prior to this, the chemical skills for refinement had existed only in Europe. This gave the opium producers control over the creation of the final product. The hundreds of thousands of American servicemen in Vietnam provided a perfect market for the heroin producers, and heroin use among soldiers rapidly increased.