There's a generally held belief that total war between two nuclear countries would begin with a massive nuclear exchange. Total war between great powers has thus become "unthinkable" due to mutually assured destruction. Almost all major powers' readiness for conventional war has atrophied enormously. What's the point of having an army if any major nuclear exchange will end the world?
Yet this seems to forget the capability for a massive biochemical exchange that existed during WWII. Yet anthrax cakes weren't spread across German fields, and London wasn't exterminated with nerve gas.
Why have nuclear weapons been treated so differently?
How likely did interwar planners think total biochemical warfare was?
What was the potential for a massive conventional war in the era since nuclear MAD became a reality?
Here is a similar question from the past with answers that will be of interest to you:
See answers by myself and u/restricteddata
Bullet point summaries from the discussion there:
Although the European theatre of WWII avoided the use of chemical and biological weapons partially to avoid retaliation in kind, the destruction would not be close to the scale of that brought about by atomic weapons in the mid-to-late Cold War.
Chemical weapons are difficult to use effectively, risk hurting your own forces, and (depending on the agent) can be counteracted by the enemy through the deployment of gas masks and body coverings.
At various points in the cold war, plans did exist to respond to conventional attacks through the use of nuclear arms, from both sides. Sometimes tactical, sometimes strategic.
Planners on both sides of the Cold War were concerned with the possibility of a "first strike" that would eliminate their nuclear capabilities. Therefore, strategic forces existed in a permanent state of high readiness to respond to an enemy attack.
As an addendum, members of the public were concerned not just with deliberate attacks, but also with accidents, glitches or incorrect identifications resulting in the assumption that an attack was imminent, and result in the launch of a counterattack against this non-existent enemy action. However, the enemy then would launch their weapons for real after the "retaliatory" attack was detected.
As restricteddata mentions, there have been and continue to be debates about whether nuclear-armed nations could fight a large conflict either without nuclear weapons at all, or whether nuclear weapons could be used tactically without resulting in strategic retaliation.
Follow up questions - did either side in the conflict have plans, now available to us, to use chemical weapons in the event another country used them and they became fair game?
Did the tech available in WWII allow for city wide destruction using chemical weapons? I mean, I'm sure massive air raids could drop poison not bombs but that seems like a lot of effort for a small reward.