A potent herbicide used from 1961 to 1971 in the Vietnam War, Agent Orange was designed to cut through Vietnam's thick canopy of foliage to reveal enemy troops beneath. While it succeeded, the price was high: exposure proved deadly to humans, causing cancers, birth defects and a slew of other disorders. Some 21 million gallons of it were dumped on Vietnam, resulting in hundreds of thousands of injuries and birth defects to Vietnamese citizens. U.S. veterans faced exposure too; they received a $180 million settlement from its manufacturers in 1984.