Lucas’s insights—first that the true definitions of international norms should be jealously guarded and not manipulated by nefarious purposes, and second that revisions to international settlements (in this instance, national frontiers) must end somewhere—are ones that Obama and other world leaders would do well to keep in mind as the Ukrainian crisis unfolds. What if all countries were permitted to intercede on behalf of neighboring coethnics? What will become of the ethnic Ukrainian and Tatar populations of Crimea if Russia assumes control there on a permanent basis? There must come a point when the extant international order—national borders, international norms, multilateral institutions—cannot be split any further. For how long can challenges to international rules be permitted until they become sustained and order itself destroyed?

“A question that vitally affects all Europe should be discussed by Europe,” Lucas urged; a plea for internationalism in an era when as small cabal of European leaders monopolized access to the levers of power. True multilateralism proved elusive during Hitler’s rise to power. Western leaders were too worried about being chain-ganged to the small states of Central and Eastern Europe to countenance truly collective security. London and Paris feared that an estranged Germany might make it harder to contain the Soviet Union. Chamberlain even fretted that war with Germany would weaken Britain’s empire to the advantage of the United States.

Today’s statesmen should not make the same mistakes. While it might be foolhardy to extend real security guarantees to the states along Russia’s periphery, a real and tangible international consensus must be brought to bear against Russian aggrandizement and the flouting of international rules. Indeed, if possible the conversation should be broadened to involve non-regional states such as China. Nonintervention and a respect for state sovereignty are the two facets of Westphalian political order that Beijing has a known and reliable interest in upholding. They are also norms that Russia has extolled in the past—over Kosovo, for example, which should make the tasks of isolating Russia and balancing against it easier to accomplish.

Despite leaders’ penchant for them, historical analogies like Munich can only be so useful. Putin is no Hitler, Ukraine no Czechoslovakia. Nevertheless, it is inevitable that leaders and pundits alike will grasp for analogies when trying to make sense of complicated crises. When they do, the history must be studied with care and the correct lessons drawn. The biggest lesson from Munich is well-worn, almost clichéd, but it would be wrong to ignore the more subtle lessons of 1938. The urge must be resisted to show resolve for the sake of maintaining credibility, to demonstrate toughness in order to save face, to construe every international incident as an opportunity to take stock of the international balance of power. At stake right now is the very fabric of international political order—that is, its legitimacy. If this is sacrificed, then the world will become a very different—and much more dangerous—place in which to live, not just for Ukrainians, for everybody else as well.

Peter Harris is a Ph.D. candidate in the Department of Government at the University of Texas, Austin, and a graduate fellow at the Clements Center for History, Strategy and Statecraft.