That all this is happening in Europe in 2022, nearly eight decades since the end of World War II and more than three decades since the collapse of the Soviet Union, is astounding. Though it was inevitable that a vast empire like the Soviet Union would not collapse without aftershocks, and these have regularly broken out in Central Asia, the Caucasus and Europe — including Russia’s annexation of Crimea — the notion of a vast seizure of territory in Europe via a full-scale war had seemed no longer possible.Yet over his many years in the Kremlin, Mr. Putin seemed to nurture an ever stronger grievance over Russia’s, and his own, treatment in the West. And at some point last year, with his personal power effectively secured for the rest of his life, with the United States bitterly divided and seemingly tired of foreign wars, with NATO seemingly at odds, Mr. Putin evidently decided it was time to spread his rule over territories he convinced himself belonged to Russia.What his calculations have evidently missed is that, whatever their history with Russia, Ukrainians have demonstrated no interest in getting under Moscow’s roof again. And the more Mr. Putin bullies them, the more strongly Ukrainians come to identify as Ukrainians.Mr. Putin also seemed to overlook that Western democracies and the Western alliance, whatever their problems, remained capable of uniting against a common threat, and of joining together to threaten him and his country with debilitating economic and social damage. The White House has also done a good job of disclosing what its intelligence is gleaning about Russia’s tactics and intentions, repeatedly underscoring the cynicism of Russia’s claims.The showdown is far from over. There are more feints Russia could make short of sending tanks across the border, including the sort of trouble it’s creating in eastern Ukraine or cyberattacks, like the one Western officials believe it recently made against Ukrainian banks.Mr. Biden and his allies and partners have been right not to overreact, and to continuously offer Mr. Putin an exit strategy. High-level meetings have been scheduled; Mr. Biden has expressed readiness to meet Mr. Putin again; the leaders of Germany and France are in constant contact with him.A wary patience at this point is not the same as appeasement, of which the Ukrainian president, Volodymyr Zelensky, accused the West. Whatever Mr. Putin’s end game, his moves for now seek to prod and provoke Ukraine and its Western friends into just the kind of overreaction the hawks advocate. There is no justification for Russia’s recognition of the two comical “peoples’ republics,” an action as illegal as it is outrageous, but the cataclysm that would befall Ukraine and Europe in the event of a full invasion warrants continuing to give diplomacy a chance.