Eliot Cohen: Trump fails his rendezvous in France.

The hardheaded interests at stake in European peace informed the moves even of the great presidential idealist Woodrow Wilson. He famously called for the world to “be made safe for democracy,” not only in light of democracy’s inherent value, but because “such a concert of free peoples” would “bring peace and safety to all nations,” including our own. “No peace can last,” Wilson said, “or ought to last, which does not recognize and accept the principle that governments derive all their just powers from the consent of the governed.”

Peace-seeking Americans, wishing to be free of German submarine warfare, seeking to enjoy the benefits of free travel and open commerce, had to fight for democracy.

Some 40 million casualties later, including 116,000 Americans killed, the United States lost its patience. It was done defending European friends, unwilling to serve as the peacekeeper of last resort. America withdrew from the continent, demobilized its forces, and isolated itself. That seemed the safest course for America; in retrospect at least, it obviously was not.

By 1940—a year before Pearl Harbor and Hitler’s declaration of war against the United States—Franklin D. Roosevelt was sounding the alarm about a possible British defeat in Europe and its implications for Americans. Should the British fall, he said, “the Axis powers will control the continents of Europe, Asia, Africa, Australasia, and the high seas—and they will be in a position to bring enormous military and naval resources against this hemisphere … All of us in the Americas would be living at the point of a gun—a gun loaded with explosive bullets, economic as well as military.”

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Another world war fought and won, American leaders resolved not to replay the catastrophic half century of European history. There would be no withdrawal this time, and no demobilization, especially in light of Moscow’s drive for domination. Nor would the United States go it alone.

Washington led the establishment of NATO to keep, in the words of Lord Ismay, “the Soviet Union out, the Americans in, and the Germans down.” And so it has. Moscow never went to war in NATO territory; Europe emerged as America’s chief trading, diplomatic, and military partner; Germany evolved into a benign power unrecognizable to Bismarck or the Kaiser or the Third Reich. And America stayed.

Such are the reasons why the United States has defended Europe for seven decades, and fundamentally why it should continue to do so today.

Yes, it can be maddening when our European allies let their militaries atrophy and devote insufficient sums to defense spending. The United States has global interests and global security commitments; it defines not just Europe but the Middle East and Asia as strategically important. A militarily successful and politically sustainable NATO alliance depends on European allies bearing a fair share of the burden. In response to Trump’s criticisms, our allies have in fact moved their defense budgets in the right direction.