Nationalism was thus one impulse in this general movement. Others were love of freedom, desire for a more democratic system, economic hopes for greater prosperity through ties to Western Europe and simple human decency. The Ukrainians inspired by these aims have just sustained an (inevitable) defeat in Crimea, but they still govern most of Ukraine, which is now escaping from Moscow’s post-Soviet institutions. While that remains the case, Mr. Putin has suffered a reverse overall.

If Ukrainian nationalists have been reactive, even victimized, in this crisis, what about Mr. Putin himself? His actions have certainly been objectionable—ruthless, aggressive, deceitful, illegal, repressive, subversive. But to describe them as “nationalist” is to reduce the concept of nationalism to a politics of aggressive self-assertion. There is no reason to suppose that nations and nation-states are more prone to indulge in such folly than are federations, empires or states founded on nonnational principles.

Mr. Putin has indeed acted ruthlessly of late, but he has done so in the service of what he sees as clear state or even personal interests, not from a commitment to Russian peoplehood.

The history of the 1930s is instructive for making the necessary distinctions here. World War II began as the result of a conspiracy by Hitler and Stalin—the Nazi-Soviet Pact—to invade Poland and divide Eastern Europe and the Baltic states between them. Nazi Germany was a state built upon the ideology of racial nationalism (which places race above nationhood), the Soviet Union upon the ideology of proletarian internationalism (which rejects nationalism entirely). Both acted far more brutally and unrestrainedly than any conventional nation-state of the period.