Full-scale war began again in Cambodia in December 1978 when the Vietnamese army invaded to overthrow the Khmer Rouge. Khmer Rouge troops retreated to border areas. In January, the Vietnamese reportedly attacked Khmer Rouge troops holed up in the temple, but there were no reports of damage to it. Large numbers of Cambodian refugees entered Thailand after the invasion. Guerrilla warfare continued in Cambodia through the 1980s and well into the 1990s, hampering access to Preah Vihear. The temple opened briefly to the public in 1992, only to be re-occupied the following year by Khmer Rouge fighters. In December 1998, the temple was the scene of negotiations by which several hundred Khmer Rouge soldiers, said to be the guerrilla movement's last significant force, agreed to surrender to the Phnom Penh government.