strengthened by large quantities of Chinese-made military equipment, which included fighter aircraft, patrol boats, heavy artillery, anti-aircraft guns, trucks and tanks. Additionally, there were between 10,000 and 20,000 Chinese advisers in both military and civilian capacities, providing their support to the Khmer Rouge government. Finally, China's PLA stationed a few hundred thousand soldiers on its own border with Vietnam (which would eventually be deployed in the brief Sino-Vietnamese War), as well as nearly two million soldiers in its border with the Soviet Union. Invasion of Kampuchea On 21 December 1978, Kampuchea's new-found strength was tested when a Vietnamese offensive, consisting of two divisions, crossed the border and moved towards the town of Kratie, while other support divisions were deployed along local routes to cut off the logistical tail of Kampuchean units. Despite enjoying generous support from China, the KRA could not withstand the Vietnamese offensive and suffered heavy casualties. On 25 December 1978, Vietnam launched a full-scale invasion using 13 divisions, estimated at 150,000 soldiers well-supported by heavy artillery and air power. Initially, Kampuchea directly challenged Vietnam's military might through conventional fighting methods, but this tactic resulted in the loss of half of the KRA within two weeks. Heavy defeats on the battlefield prompted much of the Kampuchean leadership to evacuate towards the western region of the country. On 7 January 1979, the PAVN entered Phnom Penh along with members of the KUFNS. On the following day, a pro-Vietnamese Kampuchean state, known as the People's Republic of Kampuchea (PRK), was established, with Heng Samrin as the Chief of State and Pen Sovan as General Secretary of the newly refounded Kampuchean People's Revolutionary Party. The Khmer Rouge leadership, with much of its political and military structures shattered by the Vietnamese invasion, was forced to take refuge in Thailand. The Thai government under Kriangsak Chamanan accommodated the Khmer Rouge refugees, in exchange for a promise by Deng Xiaoping to end material support to Thailand's insurgent communists. Despite the overwhelming economic challenges brought by the Khmer Rouge and the accompanying refugees, the Thai Government sheltered and protected the Khmer Rouge at Khao Larn camp in Trat Province. Meanwhile, in Phnom Penh, the new Kampuchean government tried to rebuild the country's economic and social life, which was largely destroyed by decades of political upheavals and constant warfare. However, efforts to rebuild the country were severely hampered by the lack of educated and qualified personnel,