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Editor’s Note: Susan Dunn is the Massachusetts Professor of Humanities at Williams College and the author of “A Blueprint for War: FDR and the Hundred Days That Mobilized America” (Yale University Press, 2018). The opinions expressed in this commentary are those of the author. View more opinion articles on CNN.

(CNN) —  

By attacking our closest allies and their leaders and displaying obsequious deference to the virtual dictator Vladimir Putin, Donald Trump has repudiated American global leadership. He has replaced it with a hyper-nationalism and unilateralism that are less of a foreign policy and more the bullying tactics of a would-be strongman.

Susan Dunn
Susan Dunn
PHOTO: Courtesy of Susan Dunn

Trump’s “America First” isolationism is fast weakening and isolating the United States, undermining the stability of long-standing alliances, and allowing dictatorships to thrive unchallenged around the world.

At the same time, it represents a dangerous and head-spinning reversal from decades of American conduct. Today, more than ever, we need Republican leaders who share the far-sighted and generous internationalist vision of the post-war future held in the 1940s by three exceptional Republicans: Henry Luce, the publisher of Time, Life, and Fortune; Wendell Willkie, the successful Indiana businessman who ran against and lost to Franklin D. Roosevelt in the 1940 election; and Henry Stimson, FDR’s secretary of war.

Luce published his famous article, “The American Century,” in February 1941, seven months after all the European democracies – except Great Britain – had surrendered to Hitler’s ruthless armies. Luce traced this catastrophe to the end of World War I when the Senate rejected Woodrow Wilson’s League of Nations and the United States began its retreat from world affairs.

In the 1920s and ‘30s, Americans embraced “the moral and practical bankruptcy” of isolationism, Luce wrote, and “failed to play their part as a world power.” That unwillingness to confront Hitler’s aggression in the 1930s, he underscored, brought “disastrous consequences” to “all mankind.”

But in early 1941, with strongmen like Hitler and Mussolini on the march to world domination, Luce believed that the United States still had the opportunity and obligation to exercise global leadership. The 20th century was “America’s first century as a dominant power in the world,” and if Americans rejected that global leadership, he warned, “the responsibility of refusal is also ours, and ours alone.”

Wendell Willkie shared Luce’s strong internationalist outlook. A talk he gave in 1941 could scarcely be timelier today:

“The isolationist believes that while international trade may be desirable, it is not necessary. He believes that we can build a wall around America and that democracy can live behind that wall… . . But the internationalist denies this. The internationalist declares that, to remain free, men must trade with one another – must trade freely in goods, in ideas, in customs and traditions.”

In late 1942, in the midst of the war, Wilkie embarked on a round-the-world journey, acting as FDR’s unofficial emissary, demonstrating American unity, gathering information, and discussing plans for the post-war future with key heads of state. The result was his book “One World,” a sensation that sold a million and a half copies in its first few months. The message of “One World” – the title itself was a rebuke to the very notion of isolationism – was that “this is one world; that all parts of it for their own well-being are interdependent on the other parts.”

Willkie called for a new “declaration of interdependence among the nations of this one world.” He hoped that in the postwar-world the United States would help unify and lead “the peoples of the earth in the human quest for freedom and justice.” Luce, too, envisaged the American century as powered by a “passionate devotion to American ideals,” a sharing “with all peoples of our Bill of Rights, our Declaration of Independence, our Constitution.”

Another Republican wise man, Henry Stimson, who had served as secretary of state under Herbert Hoover and secretary of war under President William Howard Taft as well as under FDR, wrote an essay in 1947 that was, in a sense, a postwar coda to Luce’s “The American Century.”

In “The Challenge to Americans,” Stimson dismissed the idea that “America can again be an island to herself.” Americans, he wrote, were now “required to think of our prosperity, our policy and our first principles as indivisibly connected with the facts of life everywhere.” And this responsible outlook, he emphasized, meant that any policy – private or public – that wasn’t framed with reference to the rest of the world “is framed with perfect futility.”

It wouldn’t be an easy task – it called for tolerance, a steadfastness of purpose, and, above all, the lucid and pragmatic recognition that “we are forced to act in the world as it is, and not in the world as we wish it were.”

More than 200 years ago, in his farewell address, George Washington spoke of his hope that the United States, as “a free, enlightened, and at no great distant period, a great nation,” would “give to mankind the magnanimous and too novel example of a people always guided by an exalted justice and benevolence.”

And to ensure the security of that magnanimous nation, he urged Americans to remain on their guard. “Against the insidious wiles of foreign influence, (I conjure you to believe me fellow citizens) the jealousy of a free people ought to be constantly awake; since history and experience prove that foreign influence is one of the most baneful foes of Republican Government.”

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If they were alive today, Luce, Willkie, and Stimson would be shocked by Donald Trump’s “America First” foreign policy and his cozying up to the impenetrable Russian autocrat. But where are the Republican wise men of today, the patriots who cherish our republic and embrace its foundational values, who believe in global interdependence and American benevolence, who repudiate unilateralism and isolationism and yet who remain vigilant, as Washington wisely said, “against the insidious wiles of foreign influence”?

Unless they play a more responsible, active and outspoken part in upholding American democracy today, they will be held accountable by history.