President Harry Truman sits at his desk on Feb. 3, 1949, surrounded by students from countries helped by the Marshall Plan. (Harvey Georges/Associated Press)

Daniel Fried, a former National Security Council director for Presidents Bill Clinton and George H.W. Bush and assistant secretary of state for Europe, is a Distinguished Fellow at the Future Europe Initiative and the Dinu Patriciu Eurasia Center at the Atlantic Council.

The “Free World Order,” the world the United States built after 1945, is under pressure from adversaries and skeptics. Nonetheless, it remains the best organizing framework for humanity. The principles behind the free world are no “globalist” plot but have deep roots. As Americans realized our strength at the beginning of the 20th century, we sought a rules-based, open world, in contrast to Europe’s closed empires. We believed that as democracy and the rule of law advanced, so would our interests. And we assumed that our nation would prosper most when other nations did as well.

This broad understanding of the national interest, rooted in values, made us exceptional. After two world wars, America and Europe built an order based on free world ideals, and the results were spectacular: the longest period of general peace in the West since Roman times, and the greatest-ever period of mass prosperity and democratic governance, both spreading, if unevenly, in the world.

What went wrong? Why such self-doubt? First, we experienced hard times. Years of slow or uneven growth, high unemployment in Europe and Gilded Age levels of income inequality in the United States generated a reaction. Add to this the challenges of national identity in the face of increasing immigration to Europe and the United States, which historically generates nativism. And finally, Russia is again acting as a corrosive political spoiler, malign by intention, using aggression, propaganda, election interference, and other “active measures” updated for the cyber age. Moscow’s objective is the same as in Soviet times: to weaken the West and its values, thus shielding Moscow’s despotic system from democratic influence and helping Russia to dominate of its neighbors.

The free world order is now challenged by a new nationalism, which rejects on principle an open, rules-based world; prefers zero-sum bilateral relations; and loathes transnational solidarity and cosmopolitan values. The nationalist idea has power and many powerful friends in Moscow, Europe and even Washington. But if America were to abandon the free world order, a world based on spheres of influence would follow, and things would get uglier, fast, as America diminished to just another great power, taking its cut. Such a system would be neither peaceful nor stable, as regional wars multiplied and the great powers argued and fought over their respective spheres, as they always do. Those who advocate a return to pre-1914 Europe or 1930’s Asia would throw away lessons that cost millions of lives to learn.

What then must we, who believe in the free world, do? In the short run, we must turn back Russia aggression. We must help the Ukrainians defend themselves, maintaining and possibly intensifying sanctions while pushing for a settlement that restores Ukraine to the Ukrainians. And we must work through NATO and the European Union to resist Russian leverage, both military and energy, and to expose Russian propaganda, dirty money and election interference. Developing a positive agenda with Russia can be useful as long as we don’t expect too much and don’t pay the Russians extra for cooperation.

Even more important, however, the free world needs to deliver economically for its people and the world. Common pro-growth policies on both sides of the Atlantic are critical.

We must also challenge the new nationalism with a new patriotism. Neither Americans nor Europeans will give up the nation state — this is where most of us find our home and identity. But the nation state is not an ultimate end. In the Western tradition, tyrannical states lose legitimacy and states gain it as they act in accordance with higher principles. Thus, we embrace the France of “Liberty, Equality, Fraternity” and find compelling the old cry of Polish patriots, “For your Freedom and Ours.” The West needs to make room for patriotism in this liberal form, bound to higher principles. And we should define the nation based on cultural, linguistic and civic, not ethno-tribal, terms.

This is the American way. As Lincoln once said, immigrants become “blood of the blood, and flesh of the flesh” of the Anglo-Saxon founders as they commit to American principles. This is also an approach that has something to offer Europe. This is not easy, as America’s history shows. But given demographic realities, a dynamic definition of the nation is critical if Europe and the United States are to integrate our newcomers.

Most important, we need to recommit to the ideals of the free world. We must make the case that our interests are best served when our values advance; that these values include the rule of law at home and a rules-based world, human rights and democracy; that our nations’ successes depend on the success of others; and that the nation state, and the free world itself, are not ends in themselves but earn legitimacy as they serve these higher purposes.

We have agency and responsibility commensurate with that agency. It is our task to rediscover our faith in our best traditions and to act to preserve, defend and extend that legacy.