In order to purge the Eastern Military Zone of those he perceived to have been contaminated by the Vietnamese, Pol Pot ordered military units from the Southwest Zone to move into eastern Kampuchea and eliminate the "hidden traitors". Unable to withstand an attack from the Kampuchea Government, So Phim committed suicide while his deputy Heng Samrin defected to Vietnam. On 12 April 1978, the Kampuchean government declared they and Vietnam could negotiate again if the Vietnamese gave up their expansionist ambitions and recognised Kampuchea's sovereignty. However, there was also a pre-condition requiring Vietnam to meet several obligations through a seven-month trial ceasefire. The Vietnamese government immediately rejected the demand. In response, two KRA divisions penetrated up to into Vietnamese territory and massacred over 3,000 Vietnamese civilians in the village of Ba Chúc in An Giang Province.