What does the United States want to be to the world? And what would the world like? A welcoming beacon of democracy? A partner in trade and security? A wary, but distant ally? Or a fortress that has pulled up its drawbridge?

For America’s allies and foes alike, the messaging of the last week has been unequivocally the latter: President Trump announced punishing steel and aluminum tariffs. He traveled to the California-Mexico border to view a border-wall prototype. And he abruptly replaced Secretary of State Rex Tillerson with the more hawkish Mike Pompeo.

Cue the drawbridge.

This isn’t the first time the United States has taken such a stern line. When Donald Trump talks about “putting America first” he echoes a deeply ingrained attitude in American foreign policy dating back to the Revolution: that the United States should look to itself and be wary of entanglements with the world beyond. Such isolationism has been a recurring force in shaping American foreign relations.

Yet there is another, quite different, and equally long-standing view: that the United States, with its enormous privileges and wealth, has an obligation to set the rest of the world straight. Sometimes that means being an example, “the shining city on the hill” as an early governor of Massachusetts put it. It can also mean using American economic, political and military power to promote democratic ideals and make the world a better place.

We tend to talk of nations as though they are individuals with defined characteristics and views on the world. It is a convenient shorthand. Nations, of course, comprise many different groups with different ideas that evolve and change over time. From the moment of its creation out of the 13 colonies, the United States has swung between wanting to keep the rest of the world at bay and itching to set it straight, between economic self-sufficiency and engagement in trade and investment, or between welcoming the world’s immigrants—those huddled masses referenced on the Statue of Liberty’s inscription—and keeping them and their dangerous foreign ways out.

“America’s journey through international politics has been a triumph of faith over experience,” said Henry Kissinger, who served as the Secretary of State under President Richard Nixon. “Torn between nostalgia for a pristine past and yearning for a perfect future, American thought has oscillated between isolationism and commitment.”

Not all countries have had the luxury of choosing. If you are Poland, surrounded by potentially hostile powers, or Canada or Mexico, with a superpower on your border, there are geopolitical realities that prevent you from isolating yourself from the rest of the world.

Geography has played a large part in fostering American isolationism. From the perspective of America’s heartland, the rest of the world can seem very far away. Ever since the 19th century, when the United States pushed its borders out to the Pacific and down into Mexico, the country has been buffered from the outside world by its sheer landmass. Canada, originally a set of small weak colonies, and Mexico, torn with internal dissent, have never been threats.

Geography smiled further on the United States. Its rich resources and ever-increasing internal market have historically limited its economic dependence on the rest of the world. Even after 1945, when the U.S. emerged as the world’s most powerful economy, most of its trade and investment was within its own borders. And when you add to that two vast oceans on either side, America, unlike most other countries in the world, has had little to fear from foreign invaders for much of its history. (That has not prevented sudden panics from seizing Americans.)

It was only in the 1940s that airpower and mechanized navies allowed then-enemies Japan and Germany to bring war to America’s shores. In the Cold War after 1945, the prospect of nuclear weapons delivered by long-range bombers or rockets finally brought an acute sense of vulnerability to Americans.

History, too, played its part in shaping U.S. attitudes. On the isolationist side of the scales, the very act of rebellion by the 13 colonies was a turning away from the old, corrupt European powers. “We have it in our power,” wrote Thomas Paine, “to begin the world over again.” For many of his contemporaries, that meant staying aloof from other nations in order to preserve American exceptionalism. In his famous Farewell Address, President George Washington warned against what he called “entanglements” and against permanent foreign alliances: “Europe has a set of primary interests which to us have none or a very remote relationship. Our detached and distant situation invited and enables us to pursue a different course.”

From the American Revolution onward, the intellectual ancestors of today’s American Firsters tended to view Europe, particularly Britain, as a threat. In the early days of the Republic, the Redcoats fought to quell its rebellious colony. In the Napoleonic Wars the British invaded the American mainland and burned the White House. During the Civil War and again in the 1890s there was talk of war between the United States and Britain.

Americans also feared “dangerous” ideas that might subvert its values and, worse, win over citizens’ hearts and minds. In the 19th century, when Roman Catholicism was the enemy, a Texas newspaper warned in 1855, “It is a notorious fact that the Monarchs of Europe and the Pope of Rome are at this very moment plotting our destruction and threatening the extinction of our political, civil, and religious institutions.”

A century later, as the Cold War raged, you could substitute Communists for Catholics: The fear was much the same, and helped to fuel isolationism.

Yet the United States has never been able to insulate itself completely against the rest of the world—and there were many Americans who did not want to do that. Among the founding fathers, even George Washington admitted that his country might occasionally need temporary military alliances. Thomas Jefferson was likewise wary of “entanglements,” but believed in the value of trade to link nations peacefully: “Commerce with all nations, alliance with none, should be our motto.” Alexander Hamilton went a step further: The United States needed to be strong economically to ensure its safety and well-being, and that might mean making deals with other powers.

American leaders were also obliged to pay some attention to their own neighborhood—if only to keep others out. The famous Monroe Doctrine, issued in 1823, was initially designed to warn Russia off expanding its colonies in the Pacific Northwest, but over the years it became a general warning to all outside powers to stop meddling in America’s backyard. When President Theodore Roosevelt issued his corollary in 1904, it became the justification for a series of military interventions in and around the Caribbean to protect American interests. In 1914, the opening of the Panama Canal served to intensify American interest in the whole region just south of its borders.

Other forces impelled the U.S. out into world. The same spirit that took the pioneers westwards took Americans around the globe. Sailing ships criss-crossed the Atlantic and ventured to the Far East looking for trade and profits. American missionaries, motivated to better the world, spread out in the 19th century to the Middle East, Africa, China and India. And when they returned, they preached that the United States had a moral obligation to engage with the rest of the world.

In the late 19th century the United States increasingly projected its growing power beyond its shores. The 1898 annexation of the Hawaiian Islands merely formally recognized what had long been American domination. The Spanish-American War the same year confirmed American dominance of the Caribbean, giving it control of Puerto Rico and, temporarily, Cuba. Even more importantly, possession of the Philippines moved the sphere of interest of the United States far out into the Pacific. Theodore Roosevelt’s policy to build a two-ocean navy confirmed that the old-style isolationism of the founders had not survived the modern, increasingly globalized world.

It took a world war, between 1914 and 1918, to draw the United States into a deeper and more sustained relationship with the wider world. President Woodrow Wilson, who had hoped to keep out of the war started in Europe, was by 1917 convinced that Germany was a menace to the future of world peace. In line with its longstanding traditions, the United States entered the war as an associate—not an ally—and Wilson insisted that its goal was to build a better world, “safe for democracy.” Like Jefferson, he saw the United States as a model for humankind; but unlike Jefferson, he believed the U.S. had to engage in the war and in the peace to come to create a new world order. The vehicle he hoped would bring nations together to make common cause for peace and prosperity was the League of Nations.

It wasn’t to be. Although many Americans, perhaps a majority, supported the League, Wilson couldn’t get the support he needed in the Senate, so the United States itself did not join. The subsequent decades of the 1920s and 1930s are often seen as the triumph of American isolationism. A powerful lobby headed by distinguished figures such as Charles Lindbergh and Henry Ford promoted America First. Congress raised tariffs to keep foreign goods out, limited immigration and, in the 1930s, passed a series of neutrality acts to ensure that the U.S. sat out future wars.

Again, however, that was only part of the picture. American diplomats worked closely with the League of Nations. The United States used its considerable influence to settle some of the outstanding issues left over from World War I, and Washington took the lead in negotiating naval limitations in the Pacific. As the world moved toward war again in the late 1930s, the United States under President Franklin Delano Roosevelt gradually tilted its financial and military support toward the democracies. In December 1941 Japan’s attack at Pearl Harbor and Hitler’s subsequent declaration of war brought the United States into the greatest and most sustained engagement with the rest of the world in its history.

When that great conflict ended, Americans again faced the choice between more or less engagement with the world. President Roosevelt and many Americans, both Democrat and Republican, hoped to prevent a new wave of isolationism by ensuring that America joined the new United Nations. In any case the decision in favor of involvement in world affairs was effectively made for them by the aggressive moves of the Soviet Union in Europe and the Middle East. The Cold War saw decades of American military, political and economic involvement around the world in what was truly a global struggle. The oscillation Henry Kissinger talked about was always there, of course, and Americans had widely different ideas about where, why and how much they should be involved. For many, faraway wars like those in Korea and Vietnam were hard to justify.

With the end of the Cold War at the start of the 1990s, the debate took on new meaning. Could the United States now safely withdraw from its alliances, friendships or partnerships? Or, as Iraq or Afghanistan might suggest, could it best defend itself by fighting battles far from the United States itself? And did Americans still have a moral duty to try and help the rest of the world, by spreading democracy? The context changes, but the debate about America’s role in the world continues to rage.

Margaret MacMillan is a former Warden of St Antony’s College, Oxford University and a professor of History at the University of Toronto. She is the author of several books on international history including Paris 1919: Six Months that Changed the World; Nixon and Mao: the Week that Changed the World; and The War that Ended Peace: the Road to 1914.

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