"In the world of strategic studies, there has been a return to ‘theories of [nuclear] victory’. Their proponents draw on the work of past scholars such as Henry Kissinger, who wondered in his 1957 book Nuclear Weapons and Foreign Policy if extending the American deterrent to all of Europe at a time when the threat of total destruction hung over the US itself would actually work: ‘A reliance on all-out war as the chief deterrent saps our system of alliances in two ways: either our allies feel that any military effort on their part is unnecessary or they may be led to the conviction that peace is preferable to war even on terms almost akin to surrender ... As the implication of all-out war with modern weapons become better understood ... it is not reasonable to assume that the United Kingdom, and even more the United States, would be prepared to commit suicide in order to defend a particular area ... whatever its importance, to an enemy’.

One of the recommended solutions was to bring tactical nuclear weapons back into the dialectic of deterrence extended to allied territories, so as to give US decision makers a range of options between Armageddon and defeat without a war. Global deterrence was ‘restored’ by creating additional rungs on the ladder of escalation, which were supposed to enable a sub-apocalyptic deterrence dialogue — before one major adversary or the other felt its key interests were threatened and resorted to extreme measures. Many theorists in the 1970s took this logic further, in particular Colin Gray in a 1979 article, now back in fashion, titled ‘Nuclear Strategy: the case for a theory of victory’.

...

In 2018 Admiral Pierre Vandier, now chief of staff of the French navy, offered a precise definition of this shift to the new strategic era, which has begun with Russia’s invasion: ‘A number of indicators suggest that we are entering a new era, a Third Nuclear Age, following the first, defined by mutual deterrence between the two superpowers, and the second, which raised hopes of a total and definitive elimination of nuclear weapons after the cold war’" [1].

I think the chances we see a tactial nuclear exchange in our lifetimes has gone from distant to almost certain.

[1] https://mondediplo.com/2022/04/03nuclear