Between 1967 and 1972, the U.S. military ran Operation Popeye, a classified weather modification program during the Vietnam War. Flying over 2,600 tactical sorties, the 54th Weather Reconnaissance Squadron dropped silver iodide flares into monsoon clouds over Laos, Cambodia, and Vietnam. The objective was strategic sabotage: flood the Ho Chi Minh Trail, trigger massive landslides, and drown North Vietnamese supply lines.
The science worked. Silver iodide crystals forced supercooled moisture to freeze and fall as intense rainfall. This cloud seeding extended the regional monsoon season by 30 to 45 days, turning dirt roads into impassable quagmires and washing out key river crossings.
