After the Great Nuclear War, the PRC was void, with no legitimate successor. Manchuria rose in the North-East, whilst Mongolia, previously a Soviet Satellite, used the lack of communications to break free, and expanded to Inner Mongolia, formally a Chinese Province.. However, from 1980, as the Soviet Union began to solidify, they wished to increase their influence in China, particuarly to the Yellow Sea.
In 1987 the Soviet Union attacked the Chinese successor states of Mongolia and Manchuria using short range missile launchers and bomber planes to attack and destroy key roads, along with communications towers, military bases and other resources necessary to put up a organized military resistance against the USSR's armed forces. This effort payed off in the USSR's campaign into northern Mongolia, in which Mongolian forces were only able to put limited resistance due to there lack of ammunition, food, manpower, and any infrastructure to transport more of any three of these resources to the frontline.
However, in Manchuria a brilliant strategist in guerrilla warfare named Lu Kong managed to hold back the Soviet army, using carefully planned ambushes on Soviet supply convoys. However, unfortunately for the Manchurians, the Soviets had a work around having working Planes still they just started flying in supplies rather than driving them to frontline severely hurting moral within the Manchurian Ranks.
Further blows to Manchuria in 1988, when the Soviet Union launched a massive naval attack against Manchuria's almost nonexistent navy. During this naval campaign, the Soviet Navy destroyed the small Manchurian Navy, blockaded Manchurian Ports, and stopped all Trade with Manchuria. This lack of any Manchurian Naval presence allowed the Soviet Aircraft Carriers SS Kiev and SS Kursk to move into position off the coast Manchuria and conduct Air Raids on Manchurian Infrastructure, Industrial Complexes, Government Facilities and other locations, including, more controversially, Religious locations in order to weaken the people's moral. The people also turn against the Manchurian Government when it is revealed that they started the war by shooting down a Soviet Jet that was flying over international waters, Thus, in southern Manchuria a large Communist Revolution began, with the "Rebels" sizing many key roads in the area along with 2 large Ammunition Factories by force in order to cripple the Manchurian army.
However, in 1989. the Soviet Union suffered its first and only major defeat of the war at the hands of Lu Kong. Lu's troops attacked a large Soviet Base under the cover of darkness, using secret tunnels to get very close to the Soviet Defenses, and then attacking at dawn, overwhelming the Soviet Defenders. Despite the victory, however, the Manchurians also took many losses.