While Prince Sihanouk was traveling in Moscow and Beijing, his own defense minister General Lon Nol seized power in Phnom Penh with backing from Cambodia's National Assembly. The coup ended Cambodia's fragile neutrality in the Vietnam War, aligning the country with the United States and setting off a chain of events that would draw Cambodia into civil war and pave the way for the Khmer Rouge's rise.
Prince Norodom Sihanouk had spent years trying to keep Cambodia neutral amid the raging war next door in Vietnam, quietly tolerating North Vietnamese and Viet Cong sanctuaries along the border while publicly maintaining independence from both Cold War blocs. That balancing act finally collapsed on March 18, 1970.
With Sihanouk out of the country, General Lon Nol and Deputy Prime Minister Sisowath Sirik Matak pushed through a vote in the National Assembly stripping the prince of power. Lon Nol's new government immediately aligned with Washington and Saigon, demanding North Vietnamese forces leave Cambodian soil.
The consequences proved catastrophic. Sihanouk, exiled and enraged, threw his support behind the communist Khmer Rouge, an insurgency he had previously suppressed, giving them legitimacy among rural Cambodians. American and South Vietnamese forces invaded Cambodia weeks later. The ensuing five-year civil war devastated the country and culminated in the Khmer Rouge's 1975 victory and the genocide that followed, killing an estimated 1.7 to 2 million people.
Key people: Lon Nol, Norodom Sihanouk