In 1911, the British writer Sydney Brooks—a regular contributor to Harper’s—suggested that America was a geographically cosseted nation and that its understanding of international politics was blunted by its relative security (a theme recently revisited by John Mearsheimer in The National Interest). Americans “live in an atmosphere of extraordinary simplicity, spaciousness, and self-absorption, until from very boredom they are forced to make international mountains out of molehills, a diversion which by itself is proof enough of their unique immunity from the serious realities of Weltpolitik,” Brooks wrote.

The exponential growth of American power soon caused Europeans to adjust their opinions about the American capacity for realpolitik. As pressure grew on the United States to enter the war in 1916, Walter Weyl, the editor of the fledgling New Republic and one of the intellectual fathers of the progressive movement, returned from a trip to Europe with some advice for his countrymen. “They ascribe to us more foresight than we possess, not realizing how often we have happily blundered into success, how often we have pursued Realpolitik in our sleep.” To illustrate the point, he recounted a conversation he had with a German academic about America’s position: “‘We Germans,’ a Berlin professor recently assured me, ‘write fat volumes about Realpolitik but understand it no better than babies in a nursery.’ ‘You Americans,’ he added, I thought enviously, ‘understand it far too well to talk about it.’”

When Woodrow Wilson did eventually take America into war in 1917, some of his supporters began to style his support for democracy and liberal values as a direct assault on realpolitik. The word had begun to seep into the American press in preceding years. Like in England, it was used interchangeably with Machiavellianism, for which the El Paso Herald provided a helpful definition in 1918: “Michiavellianism [sic]—pronounced ‘mak-ee-ah-vel-eean-izm.’ A term descriptive of unscrupulous diplomacy. Derived from the name of Machiavelli, a Florentine statesman . . . Michiavellianism has been revived by the Prussian military autocracy, and is called Realpolitik.”

Wilson’s vision of politics—along with his emphasis on liberal values—was presented as a powerful alternative to the shortsighted cynicism that realpolitik seemed to denote. Wilsonianism was no longer seen as naive; it was a potent weapon in the international arena in its own right. “How curious it is that these professors of realpolitik in European chancelleries, who lately saw nothing in the President but an academist, and nothing in his phrases but dreamy vaporings of the millennium, should be changing their tune at this time!” declared the Washington Herald in April 1917. “Of course diplomats and militarists who deal exclusively in ‘facts’ and the realities of force never see much farther than their own noses.”

The irony of this was that Wilsonianism was closer to Rochau’s version of realpolitik than anyone imagined.

AS THE Great War turned in the Allies’ favor, and they began to write the victor’s version of its origins, realpolitik featured heavily in their explanations.

Sir Charles Waldstein, an Anglo-American academic with extensive experience of Germany, reiterated the common view that it had been part of the poisoning of German philosophy and political culture in the years preceding the war: “Real-Politik and Interressen-Politik were constantly in the mouths of its leaders, from the Kaiser down to the political stump-speaker.” Even the British foreign secretary, Arthur Balfour, stated in 1918 that “Realpolitik . . . has been the true and dominating doctrine of every important German statesman, German soldier, and German thinker for two generations at least.”

Liberal Germans, Rochau’s true heirs, also joined in the criticism. Father W. Foerster, an exiled German pacifist, educationalist and ethicist, said the country had succumbed to “hallucinations of ‘Realpolitik’” that were brought on by a destructive sense of national superiority:

In spite, therefore, of all our talk of “Realpolitik,” we have remained altogether incapable of assessing the surrounding world objectively, or of emerging from our own drunken egoism; and this especially because, in addition, a fundamentally false political philosophy has taught us to look upon egoism as the only true world policy.

By the end of the Great War, therefore, realpolitik was already taken to mean a variety of sins—which were long removed from anything that Rochau had written in 1853. These included militarism, illiberalism, imperialism, naked self-interest and recklessness in the international arena. Realpolitik was understood not as a science of realism but, rather, as a glaring symptom of what had gone wrong in Germany. Insofar as other nations had participated in it, they had contributed to the unprecedented death and destruction of the Great War.

First Wilsonianism, and later the construction of the League of Nations, were conceived as an antidote to the realpolitik that had seeped into international affairs in the years before 1914. Realpolitik was to remain a dirty word in the Anglo-American world in the interwar years.

THE SECOND WAY Central European realism—and realpolitik more specifically—seeped into Western political consciousness was through the wave of German emigrant intellectuals who arrived in America before and after the Second World War. This brought a raft of uniquely talented historians and theologians such as Reinhold Niebuhr, Hans Morgenthau, Fritz Kraemer, Felix Gilbert and Henry Kissinger. In addition, the Dutch American Nicholas J. Spykman, who taught at Yale, made an important contribution to the establishment of classical realist thought in postwar America.

By the outbreak of the Second World War, realpolitik was sufficiently established in the American political lexicon to no longer need elaborate definition. It had crept into discussions about Hollywood in the 1930s, as some called for an “awakened sense of Realpolitik” in the movie industry as a corrective to the “sugar-coated” endings that contributed to the decline of cinema audiences in the period of the Great Depression. In 1940, the journal American Speech included it in a list of loan words from Germany that had become increasingly prevalent in the American press in the preceding years, alongside some other unfortunate imports: Reich, gestapo and putsch.

As those who had been trained in the way of German realism recognized, it was not a word with which one would typically want to associate oneself in this period. Despite the fact that they were entirely cognizant of the Mitteleuropean origins of realpolitik, the German émigrés generally steered clear of using the term.

In his 1951 In Defense of the National Interest, for example, Hans Morgenthau largely concealed the German influences in his thought and emphasized an English-language canon of realist thinking, which included the Federalist Papers and Lord Castlereagh’s work as British foreign secretary at the time of the Congress of Vienna.

Morgenthau’s critics recognized the sleight of hand. A review in the Economist declared his book to be the latest addition to the now “considerable American library of sermons based on the theology of realpolitik.” In 1952, he was attacked by the Austrian American theorist Frank Tannenbaum, who stated that “the advocates of Realpolitik would sweep away all of our old beliefs as foolish, sentimental, and moralistic.” Carl J. Friedrich, another émigré and a theorist of totalitarianism, called Morgenthau’s book “an American version of the German Realpolitik.”

Even by the time Morgenthau expanded his views in 1960 in The Purpose of American Politics, which he defined as “the achievement of freedom,” yet another émigré, the Marxist intellectual Herbert Marcuse, wrote to him asking what “might have driven the theorist of Realpolitik to transcend Realpolitik.”

Typically, it was President Obama’s favorite philosopher, Reinhold Niebuhr, who in 1944 came closest to finding a happy medium between what he called “the most rarified heights of constitutional idealism” and “the depths of realpolitik.”

For the most part, however, anything resembling traditional German raison d’état was seized upon by the critics of the realist school as the most recent incarnation of realpolitik. Leo Strauss, another German émigré, was perhaps the most vigilant of all, comparing Machiavelli, whom he believed had lowered men’s sights, to the “teacher of evil.” In The Road to Serfdom, Friedrich Hayek wrote that if the West were to convince Germans that there was an alternative to Nazism, it would “not be by concessions to their system of thought.” According to him, “We shall not delude them with a stale reproduction of the ideas of their fathers which we have borrowed from them—be it state socialism, Realpolitik, ‘scientific’ planning, or corporativism.”

The label was hard to shake. “The advocates of a realist foreign policy are caricatured with the German term Realpolitik,” noted Kissinger many years later, “I suppose to facilitate the choosing of sides.”

THE COLD WAR—and perhaps above all, the association with Kissinger—breathed new life into realpolitik and meant that the term outlasted the vituperative debates of the 1940s and 1950s. To this day, the word also enjoys a unique position in contemporary political discourse in that it is one of the few terms in international-relations theory that practitioners and diplomats both recognize and use.

In the Frontline Diplomacy archive at the Library of Congress, which contains transcripts of 1,743 interviews with senior American diplomats from the postwar era to the present day, the word realpolitik appears in fifty-seven of those interviews, often with expansive expositions as to what it means to the interviewee.