An all out attack by the Warsaw Pact of NATO, not necessarily using chemical/biological weapons, without any kind of hinsight on NATOs side, could probably succeed in taking Western Germany in the early-mid 1970s. In the 1980s, with the introduction of new weapons among NATO countries, it became more difficult to achieve such a goal.
The whole thing could of course escalate and lead to an all out nuclear war.
I have another question however:
Let's say the Soviets tried attacking Western Germany and failed in achieving a breakthrough. They were stopped beyond the Fulda Gap, never made it to Frankfurt and merely managed to take Hamburg in the North + Schleswig Holstein + Denmark. In the Southern Front Greece was overrun, while Turkey decided to go neutral.
This "limited victory" scenario is very plausible if the Soviets did strike with little warning on NATOs side, they could simply outnumber NATO troops and advance withing Western Germany for the first couple of weeks, until the Americans came to the rescue.
Did NATO have the power to strike back and advance inside Eastern Europe?
Would NATO do it or stand back, concerned about the possibility of the Soviets using nukes on them?
How well could the Soviets motivate their Eastern Europe colleagues to fight against NATO, even after this first setback?
What would the correct timing be to try such an attack?
It appears to me, that disappointment and the desire to stand up against the Soviets inside the Warsaw Pact countries was mainly evident in the 80s. Surely there were times in the 60s and 70s, when Eastern Europeans stood up, but the main breach came later.
What would the Soviets have to lose by gambling like that?
If NATO did indeed try to counterattack, they may have been gambling to try it in order to cause a general uprise inside the Warsaw Pact. This would however mean they would actually have to try to capture areas of Eastern European countries.
With fresh Soviet reinforcements, maybe the Soviets stood a chance to smash such an offensive and then reattack?
In the end who would lose the most?