The Secret Bombing Campaign
The bombing of Cambodia began earlier and on a far larger scale than most Americans realized at the time. While Operation Menu, the secret B-52 bombing campaign ordered by President Richard Nixon, officially started on March 18, 1969, declassified Air Force data revealed decades later that bombing actually began in October 1965 under President Lyndon Johnson. Between 1965 and 1973, American aircraft dropped 2,756,941 tons of ordnance on Cambodia in 230,516 sorties hitting 113,716 sites. To put this in perspective, the Allied powers dropped just over 2 million tons of bombs during all of World War II, including the atomic bombs on Hiroshima and Nagasaki.
The United States targeted North Vietnamese Army and Viet Cong sanctuaries along Cambodia's border with Vietnam. These communist forces used Cambodian territory as safe havens and supply routes, part of the network known as the Ho Chi Minh Trail. From the American military perspective, destroying these sanctuaries was necessary to protect South Vietnam and American forces. However, about 10 percent of the bombing was indiscriminate, with thousands of sites listed as having "unknown" targets or no target listed at all.
The human cost was staggering. Between 275,000 and 310,000 people died during the 1970-1975 civil war from bombing, combat, disease, and starvation combined. The bombing was especially intense in its final phase: in just seven months in 1973, before Congress halted the campaign on August 15, American aircraft dropped 250,000 tonnes of bombs. That's nearly half the tonnage of the entire four-year Operation Menu.
The 1970 Coup and American Invasion
While Prince Norodom Sihanouk traveled abroad in March 1970, General Lon Nol deposed him in a coup. The Cambodian parliament abolished the monarchy and established the Khmer Republic, with Lon Nol as president. The new government immediately aligned with the United States and demanded that North Vietnamese forces leave Cambodian territory.
Sihanouk, furious about his overthrow, went into exile in Beijing where he allied with his former enemies, the Khmer Rouge. He urged Cambodians to support the insurgency against what he called an American puppet government. This alliance gave the Khmer Rouge significant legitimacy among rural Cambodians who revered Sihanouk.
On April 30, 1970, American and South Vietnamese forces invaded Cambodia to strike at communist base areas. The operation was conducted without the knowledge of Lon Nol or even the U.S. State Department. American officials later testified that military planners deliberately excluded diplomats from decision-making. The invasion captured large quantities of weapons and supplies but drove North Vietnamese forces deeper into Cambodia, expanding rather than containing the conflict.
News of the "secret invasion" sparked massive protests across the United States. On May 4, 1970, National Guardsmen shot and killed four students at Kent State University in Ohio during an anti-war demonstration. Ten days later, police killed two more students at Jackson State University in Mississippi. The Cambodia invasion had brought the Vietnam War's violence home to American campuses.
The Civil War
Cambodia descended into five years of brutal civil war between Lon Nol's U.S.-backed government and the Khmer Rouge insurgency. The Lon Nol regime proved incapable of effective governance. Plagued by corruption, personality conflicts, and military incompetence, the government steadily lost ground despite massive American aid and air support.
The bombing campaign, intended to support Lon Nol by destroying enemy forces, had the opposite effect. It devastated rural Cambodia and drove angry, displaced villagers into Khmer Rouge ranks. Former New York Times correspondent Sydney Schanberg observed that the Khmer Rouge would point at bombs falling from B-52s as proof that Cambodians needed to fight for their freedom. Years after the war, journalist Bruce Palling interviewed Chhit Do, a former Khmer Rouge officer, who explained their recruitment strategy: after bombing raids, cadres would take villagers to see the craters and scorched earth. "Sometimes the bombs fell and hit little children, and their fathers would be all for the Khmer Rouge," Chhit Do recalled.
The insurgency that Pol Pot himself described in 1970 as "fewer than five thousand poorly armed guerrillas scattered across the Cambodian landscape, uncertain about their strategy, tactics, loyalty, and leaders" grew to more than 200,000 troops and militia by 1973. The Khmer Rouge's military success came not from ideology alone, but from the fury and desperation of a population suffering under relentless bombardment.
Economic and Social Collapse
The war destroyed Cambodia's economy and social fabric. Rice production, the foundation of Cambodian life, collapsed from 3.8 million tons in 1969 to just 493,000 tons in 1973. Roads and rail lines were cut. Inflation spiraled out of control. More than two million people fled the fighting and bombing, crowding into Phnom Penh and other cities. The capital's population swelled beyond its capacity to provide food, shelter, or sanitation.
By early 1975, Phnom Penh was under siege. Disease epidemics swept through the overcrowded city—measles, dysentery, and malaria killed thousands. Rocket attacks hit neighborhoods randomly. The International Committee of the Red Cross, one of the few humanitarian organizations still operating in Cambodia, reported that the city was entirely dependent on external aid for food. Even drinking water became scarce in the final weeks.
The Fall of Phnom Penh
When Congress ended American bombing in August 1973, Lon Nol's forces lost their main defensive capability. The Khmer Rouge tightened their grip around the capital throughout 1974 and early 1975. By April 1975, defeat was inevitable. Foreign embassies evacuated their staff. Relief workers fled. On April 12, the United States conducted a helicopter evacuation of its embassy in Phnom Penh. Eighteen days later, on April 30, American helicopters evacuated the U.S. embassy in Saigon as North Vietnamese forces entered the city, marking the final collapse of American involvement in Indochina.
The Khmer Rouge entered Phnom Penh on April 17, 1975. Many residents initially welcomed them, hoping they would bring peace after five years of war. That hope lasted only hours. The Khmer Rouge immediately ordered the complete evacuation of the city, all two million inhabitants, including hospital patients, the elderly, and infants. Within days, Phnom Penh stood empty.
The civil war was over. What would follow would be far worse. The same bombing and devastation that had driven Cambodians to support the Khmer Rouge had also brutalized a generation of young fighters. The insurgency's leaders had developed increasingly radical plans during years of warfare. The conditions were set for one of the twentieth century's worst atrocities.
Understanding this period is essential for grasping how the Khmer Rouge came to power. The genocide that followed in 1975-1979 was not inevitable. It grew directly from the destruction and rage of this decade. American bombing, Lon Nol's failed government, and the Khmer Rouge's ruthless exploitation of suffering all combined to create the catastrophe that would consume Cambodia.