In January 1978, the East German Embassy in Hanoi received a report stating that Vietnamese tank units had fought their way into Cambodia, and could be as close as 130 km from Phnom Penh.
The following month, the East German Defense Ministry noted that the Vietnamese forces had withdrawn.
What prompted them to turn back is unclear and government documents in Hanoi that could shed light on this remain unavailable to researchers, German historian Bernd Schaefer said in an interview on Sunday.
What is known, however, is that Hanoi had hoped to see Pol Pot ousted by opponents within the Khmer Rouge ranks without Vietnam’s direct intervention, he said. When opposition appeared impossible and Pol Pot embarked on bloody purges, the Vietnamese government had to conclude that Cambodians inside the country would not be able to get rid of him, he said.
Mr Schaefer, who is a senior research scholar at the Woodrow Wilson International Center in Washington, is giving a three-day seminar this week at Meta House on Cambodia from 1965 to 1992.
He has been conducting research for a book on relations between East Asian communist countries and the superpowers during the period using, among other materials, documents from the former government of East Germany, which was on excellent terms with Vietnam throughout the 1970s and 1980s, he said.
Although Cambodians were by no means mere observers in the international chess game between superpowers, the foreign military action that so deeply marked the country in the late 1970s and 1980s often had little to do with them, Mr Schaefer said.
Having a Cambodian government on friendly terms with Hanoi has always been crucial for the Vietnamese government, and it was Pol Pot’s proven hostility rather than his mass murders or other policies that would prompt Vietnam to oust him in 1979, he said.
In the 1960s, China and Vietnam had told Pol Pot and his jungle rebels to bide their time until Hanoi had defeated the US in battle, Mr Schaefer explained.
This changed when the Lon Nol government took over in 1970, and those two countries supported the Khmer Rouge in the civil war.
But by 1974, China was eager to prevent Vietnam from expanding its influence in Southeast Asia. This suited Pol Pot, who wanted his Vietnamese allies out of Cambodia as they were no longer needed, especially since China was supplying him with arms, Mr Schaefer said.
In June 1975, Pol Pot would be greeted as a hero in Beijing by Communist Party Chairman Mao Zedong, who—according to secret Chinese records described to Mr Schaefer—treated him as his heir apparent for emptying cities to eliminate the old order.
Deteriorating relations between Vietnam and Cambodia led to a meeting in Beijing in September 1977 during which the Chinese government took Cambodia’s side. This was followed by Khmer Rouge attacks on the Vietnamese border with China’s approval.
By then, Vietnam was determined to get rid of Pol Pot. According to an East German military report dated March 3, 1978: “Vietnam is accelerating the formation of armed units comprised of Kampuchean refugees and prisoners of war currently in Vietnam.”
When in January 1979 Pol Pot was sent fleeing to the Thai border, China attacked Northern Vietnam in retaliation.
But this was more a token gesture than a full-fledged war, Mr Schaefer said. “Both sides lost 25,000 soldiers,” he added.
Had it not been for the reform movement that swept over the Soviet Bloc in the mid-1980s, Hanoi may have hesitated in 1987 to start withdrawing its troops for fear of Moscow’s disapproval, even though it could no longer afford the Cambodian operations, he said.
In 1989, as the last Vietnamese soldiers were about to leave, the Cambodian government, Mr Schaefer said, “basically abandoned Marxism and Leninism, which was remarkable.”
Neither China nor Vietnam have ever admitted that a policy of theirs had failed, he said.
Cambodia’s April 1989 constitution re-established Buddhism as the state religion and private property, and, with Prime Minister Hun Sen and Prince Norodom Sihanouk having met, reconciliation was under way.