The mass killings that took place under the reign of the Khmer Rouge were justified by an ideology that identified dissidents as “toxic”, but such a mentality was not at the root of why lower-level cadre slaughtered their fellow Cambodians, a new report argues.

The report, which appeared in the peer-reviewed journal Terrorism and Political Violence earlier this month, posed the question “Why were so many killed?”, and interviewed 58 former Khmer Rouge cadre to determine if “toxification” propaganda motivated individuals to commit atrocious crimes.

“Toxification”, the report explains, is a genocidal ideology that sees certain individuals as lethal to the perpetrator group and its ideal society, and often dehumanises the group with quasi-medical terms, like “viruses”, “microbes” or “cancers”.

Such a mentality “depicts systematic killing as permissible and necessary,” the report states.

But Timothy Williams, one of the report’s authors from the Centre for Conflict Studies at the University of Marburg in Germany, said although such an ideology was rife in Khmer Rouge propaganda, it wasn’t the core motivation for killing.

Those reasons are more nuanced, he said, and included obedience to the all-seeing Angkar, gaining status, being coerced, ensuring their own survival, or even opportunistic personal conflicts. “[Lower-level cadre] were not committed to a communist utopia at all,” he said via email.

“They had joined the regime not out of dedication to communism but often in support of Sihanouk, or in order to gain a better life or more security for themselves. And they certainly did not kill for this communist utopia.”

But toxification provided the killers with a rationale for such widespread killings.

“Without moral justification, the individuals would be in a constant quandary,” the report read.

For Dr Ly Sok Kheang, director of DC-Cam’s Anlong Veng Peace Centre, the report’s conclusions confirmed what he already knew from his own constant questioning.

“The Khmer Rouge trained their cadre how to follow steadfastly the Khmer Rouge policies,” he said. “That’s why the people just followed without question, or because of the brutality or because of the pressure.”

“Some cadre tried to please their superiors by going beyond the policy.”

He added the leaders kept tight control at all levels and enacted widespread, systematic purges to maintain that grip on power.

Dr Sotheara Chhim, executive director at the Transcultural Psychosocial Organisation, said the Khmer Rouge also fostered an atmosphere of baksbat – “broken courage” – which led individuals to fear for their lives if they disobeyed orders.

“When they fear, they become submissive, they give in and are more obedient,” he said in an email.

“Thus they do things based on emotion, not based on cognition.”