The Soviet Union made it quite clear that were NATO to use nuclear weapons on the battlefield it would retaliate with a strategic nuclear launch against the West.

And it's that attitude that, in a perverse sense*, helped hold the enormous game of chicken in a steady state until the collapse of the USSR. Adopting the doctrine that any tactical deployment of nukes would be functionally equivalent to a strategic first strike, in essence, stabilized the European theater against border brinksmanship.

*(though no more perverse than any other aspect of post-Kissinger nuclear diplomacy)