Early in 1978, Pol Pot's government began trying to improve relations with various foreign countries, such as Thailand, to bolster its position against Vietnam. Many other governments in Southeast Asia sympathised with Cambodia's situation, fearing the impact of Vietnamese expansionism and Soviet influence on their own countries. Although supportive of the Cambodians, the Chinese government decided not to send its army into Cambodia, fearing that an all-out conflict with Vietnam could provoke a war with the Soviet Union. Meanwhile, Vietnam was planning its full-scale invasion of Cambodia. In December 1978, it formally launched the Khmer National United Front for National Salvation (KNUFNS), a group made up of Cambodian exiles which it hoped to install in place of the Khmer Rouge. Initially, KNUFNS was headed by Heng Samrin. Fearing this Vietnamese threat, Pol Pot wrote an anti-Vietnamese tract titled the "Black Paper".