In the midst of war, the United States utilized defoliants, substances that cause leaves to fall off plants when applied. These defoliants were sprayed en masse over forests in an attempt to deprive North Vietnamese forces of cover. The most notorious defoliant used during this time was Agent Orange, a mixture of two compounds called 2,4,5-T and 2,4-D in a 1:1 ratio. Exposure to Agent Orange resulted in major illnesses for over a million people in Vietnam following the war.
Defoliants were first employed as a weapon of war by Britain during the Malayan Emergency. They utilized a substance similar to Agent Orange but with the addition of a poisonous compound known as Dioxin. Dioxin was responsible for the Seveso disaster that occurred in 1976.
In addition to Agent Orange, the United States developed a combination of cacodylic acid, sodium cacodylate, and water to destroy rice crops. These plants were particularly difficult to destroy even with fire, but the mixture successfully dehydrated and killed them. The use of defoliants against civilian populations has been prohibited since 1980; however, civilians were affected during the Vietnam War. Napalm, a substance that burns easily and adheres to surfaces, was famously captured on film in 1972 by Nick Ut.
At a U.N. conference held in June 1972, Olof Palme characterized the effects of defoliants in Vietnam as “ecocide” and urged for it to be designated an international crime.