Though he initially doubted the reported scale of genocide then being perpetrated in Democratic Kampuchea, he changed his mind in 1978[1][2][3] after beginning a series of interviews with several hundred refugees from Cambodia.
His book even displays an eagerness to absolve of genocidal responsibility those members of the Khmer Rouge who defected to Hanoi and were later reinstalled in power in Phnom Penh and new-found PRK by the Vietnamese invasion of Cambodia in 1978.
Stephen J. Morris, at the time a research associate in the department of government at Harvard University, cited statements Kiernan had made regarding the Khmer Rouge in the 1970s.
Gerard Henderson, executive director of Australia's Sydney Institute, stated that Kiernan had "barracked for the Khmer Rouge when the Cambodian killing fields were choked with corpses".
[13] The Morris article was challenged by 29 Cambodia specialists who praised Kiernan as "a first-rate historian and an excellent choice for the State Department grant".