Jailed Khmer Rouge prison chief Duch explained to tribunal judges Monday the influence of Vietnam’s “Indochina Plan” in the calculations of the regime.

The guerrillas were originally supported by communists in North Vietnam, but later broke from them. By the time the Khmer Rouge were fully in power, they were opposed to the Vietnamese, and it was in part the fear of Vietnamese infiltration in the group’s ranks that led to a series of internal purges.

Duch ran Tuol Sleng prison, known to the Khmer Rouge as S-21, where many of the accused infiltrators were sent for confessions made under torture.

Duch said he appreciated the struggle of Pol Pot against the Vietnamese and a plan for Indochinese federation.

“Pol Pot was very wise in his struggle to defend Cambodia,” Duch told the judges during questioning.

Duch, 66, whose real name is Kaing Kek Iev is facing charges of war crimes, crimes against humanity, torture and murder for his role as chief of the prison, where prosecutors say more than 12,000 Cambodians were tortured and sent to their deaths.

 “I did not clearly know about the armed clashes between the Cambodian communist party and the Vietnamese communist party,” Duch said. “But I knew about armed clashes in the south of Modulkiri province and the border.”

Duch said he was not privy to decisions surrounding armed clashes, but said he put his faith in Pol Pot to defend the nascent country, which was undergoing an agrarian revolution and the policies of Democratic Kampuchea, the official name for the Khmer Rouge.

In testimony at the UN-backed court, Khmer Rouge expert Nayan Chanda described armed clashes between Khmer Rouge and Vietnamese soldiers, stemming from border disputes.