On March 19, 1970, Sihanouk was voted out of office by the National Assembly. The coup d‘état was bloodless, although later in the month pro-Sihanouk demonstrations were brutally suppressed in several provinces. Two days before the coup, Lon Nol had ordered all Vietnamese forces to leave Cambodia within forty-eight hours. Not surprisingly, there was no response, but the quixotic command reflected widespread popular opposition to the Vietnamese. When the coup took place, the prince was in Moscow on his way home. Half stunned and half enraged, he proceeded as planned on the next leg of his voyage to Beijing.

The coup seems to have taken Saloth Sar and his patrons by surprise, although the Livre noir contends that he foresaw the coup six months before it occurred and Nuon Chea, in his 1997 party history, claims that policy since 1967 had been based on the likelihood of a right-wing coup. If Sar indeed foresaw the coup, his long absence from Cambodia in 1969-1970 is difficult to explain. The Livre noir also states that in early 1970 Sar had traveled to Beijing from Hanoi “for discussions” and was thus in the Chinese capital when Sihanouk arrived on March 19. It seems more likely that Sar came from Hanoi with the Vietnamese premier, Pham Van Dong, who had been hastily summoned by the Chinese and arrived in Beijing two days after Sihanouk got there.39

The Livre noir claims that Saloth Sar persuaded the Chinese prime minister, Zhou Enlai, that Sihanouk should adopt an offensive posture toward Lon Nol and, by implication, toward the United States, reinstating an anti-American policy he had abandoned a year before. According to other sources, Pham Van Dong encouraged the prince to resist, promising to return him to power “within forty-eight hours.” Thus Sar’s advice to Zhou, if it was ever given, was identical to the advice offered to Sihanouk by Pham Van Dong. To keep Sihanouk happy and to protect the Cambodian Communists as a long-term asset, the Chinese and Vietnamese concealed Sar’s presence in Beijing from the prince, who did not identify him as the leader of the party for several years.

The anti-Vietnamese rhetoric of the Livre noir cannot conceal what must have delighted Saloth Sar in April 1970: His forces were now in a full-fledged military alliance with the Vietnamese. These unevenly endowed allies were dedicated to removing Lon Nol from power. The Red Khmer’s hopes were no longer thwarted by the exigencies of a secret, nonviolent Vietnamese-Sihanouk alliance. Instead, that alliance had now come into the open, become warlike, and was recast to include the Cambodian Communist party. The Communists could gain recruits by claiming loyalty to the prince while obtaining arms, training, and experience from Vietnam. Soon after the coup, several hundred well-trained Khmer set off from northern Vietnam to take part in their country’s struggle. Many of them had been in exile in Vietnam for fifteen years.40