Between October 1965 and August 1973, the United States conducted an increasingly devastating bombing campaign that transformed Cambodia from a neutral nation into one of the most heavily bombed countries in history. What began as limited tactical strikes under President Lyndon Johnson escalated in March 1969 when President Richard Nixon ordered B-52 carpet bombing. Over those eight years, American aircraft dropped more than 2.7 million tons of bombs on Cambodia — exceeding the total tonnage dropped by all sides during World War II. The bombing devastated the countryside, killed hundreds of thousands of civilians, and drove an enraged rural population into the arms of a previously marginal insurgent group: the Khmer Rouge.
The crisis began during the Vietnam War, when North Vietnamese forces used Cambodian territory as sanctuaries and supply routes. In 1970, a military coup overthrew Prince Norodom Sihanouk, ending decades of neutrality and replacing him with General Lon Nol, who aligned Cambodia with the United States. American and South Vietnamese forces invaded Cambodia in April 1970, sparking massive protests in the United States that culminated in the deaths of six students at Kent State and Jackson State universities.
Cambodia descended into civil war. Lon Nol's government, plagued by corruption and military failures, controlled the cities while the Khmer Rouge expanded across the countryside. The bombing campaign, intended to support Lon Nol and destroy communist sanctuaries, instead fueled Khmer Rouge recruitment. Former insurgents later testified that they would take villagers to see bomb craters, using the destruction as proof that Americans were destroying Cambodia. The Khmer Rouge grew from fewer than 5,000 poorly armed guerrillas in 1970 to more than 200,000 troops by 1973.
By 1975, Cambodia's economy had collapsed. Rice harvests plummeted from 3.8 million tons in 1969 to just 493,000 tons in 1973. More than two million refugees crowded into Phnom Penh and other cities, straining resources as rocket attacks terrorized the population. When the U.S. Congress finally halted American bombing in August 1973, Lon Nol's regime was left defenseless.
On April 17, 1975, the Khmer Rouge captured Phnom Penh. Within hours, they ordered the immediate evacuation of the entire city. The five-year civil war had created the conditions for one of the twentieth century's worst atrocities. Understanding this period helps explain how the Khmer Rouge came to power and why so many Cambodians initially welcomed them as liberators ending years of war.