Prosecutors and the defence at the Khmer Rouge tribunal yesterday presented key documents yesterday to reinforce opposing versions of events that took place between Democratic Kampuchea and Vietnam in the 1970s.

Prosecution lawyer Dale Lysak relied heavily on the research of Ben Kiernan, author of the book The Pol Pot Regime, and Khmer Rouge-era telegraphs to demonstrate that Democratic Kampuchean forces had made numerous and bloody incursions into Vietnam despite ongoing negotiations between the two neighbours.

“[While] negotiations were ongoing, Democratic Kampuchea soldiers in Mondulkiri initiated fighting and first attacked Vietnam,” Lysak said, referring to a 1976 telegram to Pol Pot and Nuon Chea, among others. Lysak also read that Cambodian forces entered Vietnam, stabbing unarmed civilians, burning villages and taking prisoners back to Cambodia.

In response, Anta Guisse, defence lawyer for Khieu Samphan, presented documents to support her argument that Vietnam didn’t recognise its border with Cambodia as legitimate, and that the Khmer Rouge had simply defended Cambodia’s sovereignty. Guisse argued that the actions of Democratic Kampuchea must be understood within the larger context of the Cold War, and ongoing talks between Hanoi and the Soviet Union about Vietnam’s borders.

As evidence that Vietnam did not respect Cambodia’s territorial integrity at the time, Guisse presented a 1976 study from the US Department of State.

“[The] question of boundary setting during the colonial period is quite important to emphasise because . . . Vietnam says that this is a border set by imperialists,” Guisse noted after reading an excerpt. “And this could be a reason for which Vietnam did not recognise this border.”

Guisse then turned to a variety of telegrams, speeches and meeting minutes to argue that the Khmer Rouge had been protecting its borders instead of aiming to invade Vietnam.

“They want to keep picking away at our territory … It is important that we prepare defence forces,” Guisse read from one such document, arguing there was no political will to attack Cambodia’s larger neighbour.

Guisse then went on to argue that the country’s experience as a member of the non-aligned movement gave it special sensitivity to questions of national integrity.