China's relations with Vietnam began to deteriorate seriously in the mid-1970s (see An Overview of China's Foreign Relations , ch. 12). After Vietnam joined the Soviet-dominated Council for Mutual Economic Cooperation (Comecon) and signed the Treaty of Friendship and Cooperation with the Soviet Union in 1978, China branded Vietnam the "Cuba of the East" and called the treaty a military alliance. Incidents along the Sino-Vietnamese border increased in frequency and violence. In December 1978 Vietnam invaded Cambodia, quickly ousted the pro-Beijing Pol Pot regime, and overran the country. In February 1979 China attacked along virtually the entire Sino-Vietnamese border in a brief, limited campaign that involved ground forces only. In March Beijing declared its "lesson" finished and withdrew all its troops (see Historical Development, 1927-79 , this ch.).
After the war, both China and Vietnam reorganized their border defenses. The border war strengthened Soviet-Vietnamese relations. The Soviet military role in Vietnam increased during the 1980s as the Soviets provided arms to Vietnam; moreover, Soviet ships enjoyed access to the harbors at Danang and Cam Ranh Bay, and Soviet reconnaissance aircraft operated out of Vietnamese airfields. Low-level conflict continued along the Sino-Vietnamese border as each side conducted artillery shelling and probed to gain high spots in the mountainous border terrain. Border incidents increased in intensity during the rainy season, when Beijing attempted to ease Vietnamese pressure against Cambodian resistance fighters. In 1986 China deployed twenty-five to twenty-eight divisions and Vietnam thirty-two divisions along their common border. Nevertheless, most observers doubted that China would risk another war with Vietnam in the near future.
Data as of July 1987