If a world war was ever to break out, conventional warfare wouldn't come into it. Some twat would launch a nuke, everyone else would retaliate and that's the end of that, adios, ciao, goodnight Vienna, later dudes!
When I was serving during the 80's the "Cold War gone Hot" strategy was all about delaying actions on each front.
To train for that, every year we went on exercise to Norway as part of the British contingent of the AMF (a multi-unit international force) where we were expected to prevent the Soviets hooking over the top of Scandinavia and using it as a springboard to attack the UK and to storm south through Denmark creating a second (or third) front to attack the bulk of NATO forces in mainland Europe. They were facing the main Soviet Juggernaut sightseeing its way through West Germany and onwards to the channel.
It was generally accepted that we would ultimately fail through attrition due to the sheer weight of Soviet numbers and at some point NATO would push the button.
That would usually begin with what was euphemistically called limited nuclear war, with the idea being that it would be enough to make the Soviets pause for thought. The reality was that it would escalate to the inevitable "buckets of sunshine" pretty quickly and we'd all be fecked.
The bit that always made me laugh was the idea that just maybe NATO land forces could give Ivan such a conventionally fought bloody nose that he might just stop, without the need to deploy the big bang stuff. Clearly indicating that the NATO headshed had not being reading up on how the Russians fought the Eastern Front in WW2.
