Their rise to power was also correlated with our presence in Indochina. Historians Ben Kiernan and Taylor Owen have used a combination of sophisticated satellite mapping, recently unclassified data about the extent of bombing activities, and peasant testimony, to argue that there was a strong correlation between villages targeted by U.S. bombing and recruitment of peasants by the Khmer Rouge. Kiernan and Owen argue that "Civilian casualties in Cambodia drove an enraged populace into the arms of an insurgency that had enjoyed relatively little support until the bombing began."
http://www.yale.edu/cgp/Walrus_Cambo...bing_OCT06.pdf