Complex sentence: While the Soviet Union hopes for an eventual Communist victory in South Vietnam, but it is more conscious than Peiping and Hanoi of the larger military risks... it does not wish the kind of Communist victory which would magnify the prestige and power of China.
Split into simpler sentences: While the Soviet Union hoped for an eventual Communist victory in South Vietnam, but it was more conscious of the larger military risks. The UUSR did not want the kind of Communist victory which would magnify the prestige and power of China.