There are paths of escalation that merely risk nuclear annihilation rather than guarantee it. In particular, in a war with NATO, where Russian forces would be heavily outmatched in conventional warfare, Russian forces would consider using "deescalatory" tactical nuclear strikes on NATO troops. The side that has the most invested (e.g. for Russia where Kyiv is seen as integral to its historical Slavic / Rus heritage) is most likely to engage in escalation and brinksmanship while the other side has to consider whether to follow it up the escalatory ladder or back down.

Putin is on record as saying "There is no world imaginable without Russia"