The image of the drug-addicted American soldier -- disheveled, glassy-eyed, his uniform adorned with slogans of antiwar dissent -- has long been associated with the Vietnam War. More specifically, it has persisted as an explanation for the U.S. defeat, the symbol of a demoralized army incapable of carrying out its military mission.

Yet as Jeremy Kuzmarov documents in this deeply researched book, popular assumptions about drug use in Vietnam are based more on myth than fact. Not only was alcohol the intoxicant of choice for most GIs, but the prevalence of other drugs varied enormously....