9. Operation Popeye
To discourage anti-Diem protests, the CIA and the US military cooked up a plan to seed clouds and make them, literally, rain on the parades of anti-Diem protestors. Doing so, it was hoped, would dampen turnout and disperse the crowds. That did not save Diem, who was overthrown and assassinated in 1963, but cloud seeding survived to be used as a tactic in the Vietnam War.
Codenamed Operation Popeye, modified cargo planes began flying over the Ho Chi Minh Trail in 1967, releasing silver and lead iodide flares. The goal was to increase the monsoon period’s rainfall, and thus negatively impact the routes used to supply and reinforce communist forces in South Vietnam. By the time Operation Popeye was terminated in 1972, over 2600 missions had been flown, during which roughly 47,000 cloud seeding charges were dropped. Their impact on the Ho Chi Minh trail and communist supplies and reinforcements were next to nil.