Pol Pot

=== Kampuchean Labour Party: 1959–1962 ===
At a 1959 conference, the movement's leadership established the Kampuchean Labour Party, based on the Marxist–Leninist model of [[democratic centralism]]. Sâr, Tou Samouth and Nuon Chea were part of a four-man General Affair Committee leading the party.{{sfn|Short|2004|pp=135–136}} Its existence was to be kept secret from non-members.{{sfn|Chandler|1992|p=62}} The Kampuchean Labour Party's conference, held clandestinely from September to October 1960 in Phnom Penh, saw Samouth become party secretary and Nuon Chea his deputy, while Sâr took the third senior position and Ieng Sary the fourth.{{sfnm|1a1=Chandler|1y=1992|1pp=61–62|2a1=Short|2y=2004|2p=138}}<ref name="Tyner">{{cite book |last1=Tyner |first1=James A. |title=From Rice Fields to Killing Fields: Nature, Life, and Labor under the Khmer Rouge |date=2017 |publisher=Syracuse University Press |location=Syracuse, NY |isbn=978-0815635567 |page=38 |url=http://syracuseuniversitypress.syr.edu/fall-2017/from-rice-fields.shtml |access-date=23 January 2019 |archive-date=14 March 2019 |archive-url=https://web.archive.org/web/20190314045834/http://www.syracuseuniversitypress.syr.edu/fall-2017/from-rice-fields.shtml |url-status=live }}</ref>

Sihanouk spoke out against the Cambodian Khmer communists; he also warned of its [[totalitarianism|totalitarian]] character and its suppression of personal liberty.{{sfn|Short|2004|pp=139–40}} In January 1962, Sihanouk's security services cracked down further on Cambodia's socialists, incarcerating Pracheachon's leaders and leaving the party largely moribund.{{sfnm|1a1=Chandler|1y=1992|1p=63|2a1=Short|2y=2004|2p=140}} In July, Samouth was arrested, tortured and killed.{{sfnm|1a1=Chandler|1y=1992|1pp=63–64|2a1=Short|2y=2004|2p=141}} Nuon Chea had also stepped back from his political activities, leaving open Sâr's path to become party leader.{{sfn|Short|2004|p=141}}

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.{{sfn|Short|2004|pp=124–25}} 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.{{sfn|Short|2004|p=127}} After Sihanouk's father died in 1960, Sihanouk introduced a constitutional amendment allowing himself to become head of state for life.{{sfnm|1a1=Chandler|1y=1992|1p=60|2a1=Short|2y=2004|2pp=131–32}} 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.{{sfnm|1a1=Chandler|1y=1992|1p=66|2a1=Short|2y=2004|2pp=142–43}} 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.{{sfnm|1a1=Chandler|1y=1992|1p=67|2a1=Short|2y=2004|2p=144}} According to Chandler, "from this point on he was a full-time revolutionary".{{sfn|Chandler|1992|p=67}}