The movement was largely made up of dissident rural peasantry led by a group of discontented leftist intellectuals against Prince Norodom Sihanouk’s political organization, the Sangkum regime.
The rebellion first erupted in early 1967 in the Samlaut subdistrict when hundreds of frustrated peasants, tired of government policies, mistreatment by local military, land displacement, and other poor socio-economic conditions.
By June 1967, four thousand or more villagers had fled their homes in southern Battambang Province into the forest to join the growing group of rebels and escape the military troops sent by Sihanouk.
The Republican government wanted to portray the Cambodian revolutionary movement as largely a foreign (mainly Vietnamese) transplant and preferred to gloss over the significance of indigenous leftist activity from 1967.
According to Chandler, the revolt “sprang from local grievances against injustice and social change, corruption, and ham-fisted government behavior” and the participants “did not respond to orders from the Communist Party of Kampuchea (CPK) central committee”.
[8][6]: 193 With the escalation of the war in South Vietnam in 1965, the colonization of Battambang entered a new phase as thousands of Khmer Krom families began to cross the Vietnam-Cambodia border.
[15][16] This system provoked an uproar by the rural population in Battambang Province where it was first introduced as many households not only saw their earnings being severely reduced due to the low prices offered for the crops but were also forcibly made to surrender their produce at gunpoint.
Centered on rapidly growing fruit plantations, it was a conflict between a ‘rich and enterprising Chinese bourgeoisie which has taken possession of the land, and the alienated, indebted, and already semi-independent village communities.”[24] According to Kiernan, it was clear that “corruption, the misuse of the military and other authority, and increasing impoverishment, in the Samlaut, Pailin and Andoeuk Hep districts, for example, created a vast reservoir of peasant unrest that lacked only a reasonably sophisticated leadership.
By early 1967, that leadership had begun to take shape and it provided, as well as a sympathetic and purposeful ideology, the guidance to enable an already disaffected peasantry to carry out a serious and effective rebellion.”[25] Vietnamese and Chinese communists played a small role in planting the seeds of rural revolt.
It is argued that some of the disturbances in 1967 were part of a coordinated effort by the leftists to destabilise Sihanouk's regime, though the official Khmer Rouge historiography given by Pol Pot later sought to deny this, stating its open rebellion only occurred in January 1968 and that the Samlaut incident was "premature"[27] and surprised the communist party[28] “The people armed themselves with knives, axes, clubs, and other weapons they could lay their hands on to attack police stations and military garrisons,” “[But] the Party Central Committee had not yet decided on general armed insurrection throughout the country.
"Armed resistance by the left broke out in April, erupting in the Samlaut area in northwestern Battambang Province, long noted for large landowners and great disparities of wealth.
(Royal Khmer Socialist Youth) agricultural settlement at Stung Kranhoung, the most obvious symbol of government presence in the area, the source of the villagers’ grievances and official mistreatment, as the target for their first organized display of force.
A platoon of paratroopers and national police were sent into the region to protect the population, allegedly having been offered a bounty for each severed head of a rebel or leftist that they sent back to Phnom Penh.
[35] Despite Sihanouk's attempts to offer amnesty to the local rebels, the rebellion spread to other districts to the north and the east, with many of the villagers fleeing to the maquis to avoid the advancing army battalion.
[36] On the eastern side of the country, seventy armed followers of CPK cadre So Phim infiltrated the town of Kandol Chrum, killed a former district chief, and wounded a government agent; Ieng Thirith, another prominent Communist, was seen in Samlaut itself.
From October 1967 onwards, younger left-wing groups from the towns, including school teachers and ex-students, stepped up their liaisons with previously dormant cells of Communist sympathizers in remote areas like southern Battambang, while others joined the maquis.
[40] Peasant support for the revolutionaries was compounded by oppressive processes such as the resumption of rammassage campaigns in late December 1967 and the government’s decision to appoint village headmen and officials directly.
[41] The central Government intervention represented a significant development in rural administrative repression by Phnom Penh, resented by many peasants who cherished the traditional autonomy of village affairs.
This led to the replacement of provincial leaders with military officials and the harsh counter-forces of Lon Nol, including the use of air force to bomb targeted rebel camps in the jungle.
However, the situation started to turn bleak for the Khmer Rouge, suffering heavier losses against an increasingly consolidated and violent army that destroyed their camps and supplies and a mobilized group of townspeople who supported Sihanouk and went against the peasants.
[53] Ultimately, all these measures increased the rural population's isolation from and resentment of the government, military and the urban elite, strengthening support for the revolutionaries as dissidence continued to persist in the following years.
[54] Since the suppression of their forces, rebels in southern Battambang began to move south-east to link up with the Khmer Rouge in other provinces like Pursat, Kompong Chhnang and Kampong Speu.
Although North Vietnam had established a special unit in 1966 to train the CPK, it was extremely reluctant to alienate Sihanouk at a time when vital supplies were passing through the port of Sihanoukville and along the Ho Chi Minh Trail to the VC bases along the Cambodia-Vietnam border.
Perhaps, the indifference of the world communist movement to the Cambodian struggle since early 1967 made a permanent impression on Pol Pot and other Khmer Rouge leaders, shaping their isolated and self-sufficient vision of Democratic Kampuchea.