Here is a quote that I find very relevant to a war in the 50s regarding OTL 1990s how the USSR would have handled it potentially
Japan's weapons research would include chemical and biological weapons of course, which makes a declaration of war by the Chinese themselves a disastrous idea during the 50s quite possibly
If Soviet forces were in danger of being overwhelmed by sheer numbers of Chinese troops, the Soviets would be likely to employ chemical weapons, against which the Chinese have little capacity to defend themselves and a limited capability to reply in kind.
Japan's weapons research would include chemical and biological weapons of course, which makes a declaration of war by the Chinese themselves a disastrous idea during the 50s quite possibly