As well as facing leftist opposition, Sihanouk's government faced hostility from right-wing opposition centred on Sihanouk's former Minister of State, Sam Sary, who was backed by the United States, Thailand and South Vietnam. After the South Vietnamese supported a failed coup against Sihanouk, relations between the countries deteriorated and the United States initiated an economic blockade of Cambodia in 1956. After Sihanouk's father died in 1960, Sihanouk introduced a constitutional amendment allowing himself to become head of state for life. In February 1962, anti-government student protests turned into riots, at which Sihanouk dismissed the Sangkum government, called new elections, and produced a list of 34 left-leaning Cambodians, demanding that they meet him to establish a new administration. Sâr was on the list, perhaps because of his role as a teacher, but refused to meet with Sihanouk. He and Ieng Sary left Phnom Penh for a Viet Cong encampment near Thboung Khmum in the jungle along Cambodia's border with South Vietnam. According to Chandler, "from this point on he was a full-time revolutionary".