As Barbara Ehrenreich reminds us, Almost any drug or intoxicant has served, in one setting or another, to facilitate the transformation of man into warrior.

Yanomam Indians of the Amazon ingest a hallucinogen before battle; the ancient Scythians smoked hemp, while a neighboring tribe drank something called ‘hauma,’ which is believed to have induced a frenzy of aggression. So if there is a destructive instinct that impels men to war, it is a weak one, and often requires a great deal of help.

The aforementioned Yanomamos, the indigenous people who lived in the Orinoco basin on the border between the today’s Venezuela and Brazil, fought ritual chest-pounding duels with neighbors at intervillage feasts. The duels were ‘always conducted between members of different villages and arose over accusations of cowardice or in response to excessive demands for trade goods, food, or women.“ The duelers, writes Keegan, 'took hallucinogenic drugs to foster a fighting mood.’

The Otomac Indians were another tribal people from the Orinoco basin whose warriors regularly got intoxicated before battle. In his book, El Orinoco Ilustrado y defendido (The Orinoco Illustrated and Defended, 1731), the Spanish Jesuit priest Joseph Gumilla tells his readers that the Otomacs would 'get fighting mad with yupa, wound themselves, and, full of blood and fury, go out to fight like raging tigers.’

Yupa was a powdered snuff extract from the seeds of the Piptadenia peregrina, a tree containing hallucinogenic alkaloids. Among the Otomacs, yupa-induced intoxication played an important ritualistic, shamanic, and therapeutic role, and also one in combat.

—  Lukasz Kamienski, Shooting Up: A Short History of Drugs and War