In 1952, at the age of twenty-eight, Henry Kissinger did what enterprising graduate students do when they want to hedge their academic future: he started a magazine. He picked an imposing name—Confluence—and enlisted illustrious contributors: Hannah Arendt, Raymond Aron, Lillian Smith, Arthur Schlesinger, Jr., Reinhold Niebuhr. The publisher James Laughlin, who was a backer of the magazine, described the young Kissinger as “a thoroughly sincere person (terribly earnest Germanic type) who is trying his hardest to do an idealistic job.” Like his other early production, the Harvard International Seminar, a summer program that convened participants from around the world—Kissinger gamely volunteered to spy on attendees for the F.B.I.—the magazine opened channels for him not only with policymakers in Washington but also with an older generation of German Jewish thinkers whose political experience had been formed in the early thirties, when the Weimar Republic was supplanted by the Nazi regime.

For Cold War liberals, who saw the stirrings of fascism in everything from McCarthyism to the rise of mass culture, Weimar was a cautionary tale, conferring a certain authority on those who had survived. Kissinger cultivated the Weimar intellectuals, but he was not impressed by their prospects for influence. Although he later invoked the memory of Nazism to justify all manner of power plays, at this stage he was building a reputation as an all-American maverick. He appalled the émigrés by running an article in Confluence by Ernst von Salomon, a far-rightist who had hired a getaway driver for the men who assassinated the Weimar Republic’s foreign minister. “I have now joined you as a cardinal villain in the liberal demonology,” Kissinger told a friend afterward, joking that the piece was being taken as “a symptom of my totalitarian and even Nazi sympathies.”

For more than sixty years, Henry Kissinger’s name has been synonymous with the foreign-policy doctrine called “realism.” In his time as national-security adviser and Secretary of State to President Richard Nixon, his willingness to speak frankly about the U.S.’s pursuit of power in a chaotic world brought him both acclaim and notoriety. Afterward, the case against him built, bolstered by a stream of declassified documents chronicling actions across the globe. Seymour Hersh, in “The Price of Power” (1983), portrayed Kissinger as an unhinged paranoiac; Christopher Hitchens, in “The Trial of Henry Kissinger” (2001), styled his attack as a charge sheet for prosecuting him as a war criminal.

But Kissinger, now approaching his ninety-seventh birthday, no longer inspires such widespread loathing. As former critics crept toward the political center and rose to power themselves, passions cooled. Hillary Clinton, who, as a law student at Yale, vocally opposed Kissinger’s bombing of Cambodia, has described the “astute observations” he shared with her when she was Secretary of State, writing in an effusive review of his most recent book that “Kissinger is a friend.” During one of the 2008 Presidential debates, John McCain and Barack Obama each cited Kissinger as supporting their (opposite) postures toward Iran. Samantha Power, the most celebrated critic of the U.S.’s failure to halt genocides, was not above receiving the Henry A. Kissinger Prize from him.

Kissinger has proved fertile ground for historians and publishers. There are psychoanalytic studies, tell-alls by former girlfriends, compendiums of his quotations, and business books about his dealmaking. Two of the most significant recent assessments appeared in 2015: the first volume of Niall Ferguson’s authorized biography, which appraised Kissinger sympathetically from the right, and Greg Grandin’s “Kissinger’s Shadow,” which approached him critically from the left. From opposing perspectives, they converged in questioning the profundity of Kissinger’s realism. In Ferguson’s account, Kissinger enters as a young idealist who follows every postwar foreign-policy fashion and repeatedly attaches himself to the wrong Presidential candidates, until he finally gets lucky with Nixon. Grandin’s Kissinger, despite speaking the language of realists—“credibility,” “linkage,” “balance of power”—has a view of reality so cavalier as to be radically relativist.

Barry Gewen’s new book, “The Inevitability of Tragedy” (Norton), belongs to the neither-revile-him-nor-revere-him school of Kissingerology. “No one has thought more deeply about international affairs,” Gewen writes, and adds, “Kissinger’s thinking runs so counter to what Americans believe or wish to believe.” Gewen, an editor at the New York Times Book Review, traces Kissinger’s most momentous foreign-policy decisions to his experience as “a child of Weimar.” Although Gewen is aware of the pitfalls of attributing too much to a regime that collapsed before his subject’s tenth birthday, he is fascinated by the connections between Kissinger and his émigré elders, whose experiences of liberal democracy made them fear democracy’s capacity to undermine liberalism.

Heinz Kissinger was born in 1923 in Fürth, a city in Bavaria. His family fled to New York shortly before Kristallnacht, settling in Washington Heights, a neighborhood with so many German immigrants that it was sometimes known as the Fourth Reich. They spoke English at home, and Heinz became Henry. In his youth, he displayed few remarkable qualities beyond enthusiasm for Italian defensive soccer tactics and a knack for advising his friends on their amorous exploits. As a teen-ager, he worked in a shaving-brush factory before school, and aspired to become an accountant.

In 1942, Kissinger was drafted into the U.S. Army. At Camp Claiborne, Louisiana, he befriended Fritz Kraemer, a German-American private fifteen years his senior, whom Kissinger would call “the greatest single influence on my formative years.” A Nietzschean firebrand to the point of self-parody—he wore a monocle in his good eye to make his weak eye work harder—Kraemer claimed to have spent the late Weimar years fighting both Communists and Nazi Brown Shirts in the streets. He had doctorates in political science and international law, and pursued a promising career at the League of Nations before fleeing to the U.S., in 1939. He warned Kissinger not to emulate “cleverling” intellectuals and their bloodless cost-benefit analyses. Believing Kissinger to be “musically attuned to history,” he told him, “Only if you do not ‘calculate’ will you really have the freedom which distinguishes you from the little people.”

For all the imputations of Kissinger’s Germanness, the indelible experience of his youth was serving in the 84th Infantry Division as it swept through Europe. “He was more American than I have ever seen any American,” a comrade recalled. The work of the U.S. occupation, with its opportunities for quickly assuming positions of authority, thrilled him. In 1945, Kissinger participated in the liberation of the Ahlem concentration camp, outside Hanover, and earned a Bronze Star for his role in breaking up a Gestapo sleeper cell.

It says it wants to do a crossword.
“It says it wants to do a crossword.”
Cartoon by Charlie Hankin

In 1947, Kissinger enrolled at Harvard on the G.I. Bill, intending to study political science and English literature. He found a second mentor, William Yandell Elliott, a well-connected history professor from the Wasp élite, who advised a series of U.S. Presidents on international affairs. The young Kissinger was drawn less to the classic exponents of Realpolitik, such as Clausewitz and Bismarck, than to “philosophers of history” like Kant and anatomists of civilizational decay such as Arnold Toynbee and Oswald Spengler. From these thinkers, Kissinger cobbled together his own view of how history operated. It was not a story of liberal progress, or of class consciousness, or of cycles of birth, maturity, and decline; rather, it was “a series of meaningless incidents,” fleetingly given shape by the application of human will. As a young infantryman, Kissinger had learned that victors ransacked history for analogies to gild their triumphs, while the vanquished sought out the historical causes of their misfortune.