Nevertheless, Putin’s cost-benefit analysis seems to favor upending the European status quo. The Russian leadership is taking on more risks, and above the fray of day-to-day politics, Putin is on a historic mission to solidify Russia’s leverage in Ukraine (as he has recently in Belarus and Kazakhstan). And as Moscow sees it, a victory in Ukraine might well be within reach. Of course, Russia might simply prolong the current crisis without invading or find some palatable way to disengage. But if the Kremlin’s calculus is right, as in the end it was in Syria, then the United States and Europe should also be prepared for an eventuality other than quagmire. What if Russia wins in Ukraine?

If Russia gains control of Ukraine or manages to destabilize it on a major scale, a new era for the United States and for Europe will begin. U.S. and European leaders would face the dual challenge of rethinking European security and of not being drawn into a larger war with Russia. All sides would have to consider the potential of nuclear-armed adversaries in direct confrontation. These two responsibilities—robustly defending European peace and prudently avoiding military escalation with Russia—will not necessarily be compatible. The United States and its allies could find themselves deeply unprepared for the task of having to create a new European security order as a result of Russia’s military actions in Ukraine.