Putin could also use NATO’s participation in the war to override objections in the Kremlin or the Russian defense ministry regarding the use of nuclear weapons. Russian elites who might quail at the idea of deploying nuclear bombs against innocent Ukrainians will be harder pressed to explain their opposition to using such weapons against the NATO air bases from which jets are flying into combat, killing Russian soldiers and turning Russia’s mighty tanks into flaming wrecks.

Although some observers may believe that Putin would fold before he approaches the nuclear threshold, and others worry that even the smallest NATO action will inevitably spark World War III, such arguments at both extremes ignore the role of chance and risk. A nuclear crisis is not an orderly duel or a game with rules, but rather a maelstrom of poor information, conflicting signals, and highly charged emotions. To make matters worse, Putin has always been a poor strategist, a risk-taker who foolishly sets in motion—as he has done in Ukraine—forces he cannot control.

In any case, even if Putin is too deluded to think about such risks, the rest of us must consider the dangers of ordering the largest military coalition in human history into battle against a disorganized and battered army led by incompetent officers and commanded by an isolated and delusional president. Putting so many military assets in play, with combat breaking out all over Europe, could spark a catastrophe that neither we nor Putin intended. The danger is not that the Russian war on Ukraine becomes a replay of 1939, in which a coalition must stop a mad dictator at all costs, but that a Russia-NATO war becomes a nuclear version of 1914, in which all the combatants would find themselves moving from a crisis none of them expected into a cataclysm none of them wanted.