The best available model of such an event is an ultrasecret 1983 Pentagon war game called Proud Prophet. That game was a nuclear test of sorts, and it provided critical lessons that remain crucial today. It was unique in that by design it was largely unscripted, involved the highest levels of the U.S. military and its global warfighting commands and used actual communication channels, doctrines and secret war plans. One of its great strengths was that unlike any other war game involving the possibility of small-yield nuclear weapons, it ran freely and was allowed to play out to its natural conclusion: global devastation.
The conclusion was a shock. The lesson drawn from it — that nuclear war cannot be controlled — had a decades-long effect on American strategy and therefore, in a world of opposing mirrors, on global strategies. It may be that someday in the future a survivor will be able to look back at our times and observe that the greatest tragedy in all of human history is that among current leaders in Russia and the United States, and perhaps other countries, the lesson was forgotten.