He had a progressive cognitive impairment, but the immediate cause was unknown, said his physician and friend, Michael Newman.
Mr. Steel, a high-profile public intellectual, was affiliated with think tanks and universities throughout his career and was a frequent contributor to the New York Review of Books, the Atlantic Monthly and other publications. A former Foreign Service officer, he established his reputation with two early books on international relations, including “Pax Americana” (1967).
In that book, Mr. Steel argued that a postwar obsession with the communist threat led to a counterproductive, financially draining U.S. military buildup. An inevitable consequence of such a foreign policy, he said, was to engage in military action rather than seek diplomatic or economic solutions to international conflicts.
Historian Henry Steele Commager, writing in the New York Times, pronounced “Pax Americana” the “most ardent and, to my mind, the most persuasive critique of American foreign policy over the last twenty years that has yet appeared.”
Mr. Steel later planned to write about Lippmann and the Cold War — a phrase first popularized by Lippmann after World War II to describe the ideological chess match between the Soviet Union and western democracies.
The project soon evolved into a full-scale biography of the prolific author and two-time Pulitzer Prize-winner whose syndicated column appeared in hundreds of newspapers.
Lippmann was a monumental figure — “without doubt the nation’s greatest journalist,” in Mr. Steel’s words — whose ideas helped define the thinking of the political establishment for decades. Mr. Steel interviewed him at length before Lippmann’s death in 1974.
“I had no idea what I was getting into,” Mr. Steel told The Washington Post in 1980. “He’d been writing three columns a week since 1931. He’d written 22 books. . . . He’d known everybody and been a critical and articulate observer of this country since 1912.”
After “Walter Lippmann and the American Century” was published in 1980, columnist Anthony Lewis, writing in the New York Review of Books, praised it as “a fascinating book: on journalism, on America in the world, on a mysterious human being.”
Lippmann had been a celebrated figure since his undergraduate days at Harvard, where psychologist William James knocked on his door, hoping to meet the student reputed to be the most brilliant on campus. Lippmann was a founding editor of the New Republic and, as early as the administration of Woodrow Wilson, began to shape the thinking of key figures at the White House.
The young wunderkind went on to become editor of the New York World newspaper before writing a long-running column based at the New York Herald Tribune. His influence became so profound that presidents came to his house for social gatherings.
“Lippmann commanded a loyal and powerful constituency, some ten million of the most politically active and articulate people in America,” Mr. Steel wrote in his 669-page biography. “Many of these people literally did not know what they ought to think about the issues of the day until they read what Walter Lippmann had to say about them. A politician could ignore that power only at his own risk.”
But Mr. Steel also discovered a deeply complex and paradoxical figure in Lippmann, who sought to conceal much of his personal history, including his Jewish background. Lippmann was excluded from social clubs at Harvard because of his heritage, yet he did not speak out against Nazi persecution of Jews during World War II.
When Mr. Steel casually asked Lippmann about his father’s occupation, “I soon learned that his definition of personal was quite broad,” Mr. Steel wrote in the Times in 1985. “He looked at me with his slightly bulging, heavy-hooded eyes for what seemed like minutes, and then said solemnly: ‘I wouldn’t want you to make a novel of this.’ ”
Married and in his 40s, Lippmann had a passionate affair with Helen Armstrong, the wife of a close friend. After two messy divorces, they were married and moved from New York to Washington. Mr. Steel learned about the affair from Helen Lippmann, who died months before her husband in 1974.
“From the love letters she let me read,” Mr. Steel wrote, “I saw a different Walter Lippmann from the one he had shown to the world, or that I was even sure existed. Here was a Lippmann who could be lyrical, passionate, awkward and even a little bit absurd. . . . Helen Lippmann helped me glimpse a man no one but she really knew.”
“Walter Lippmann and the American Century” won the National Book Award and the Bancroft Prize, presented each year by Columbia University to an outstanding scholarly work of history. In 2000, historian Joseph J. Ellis hailed the book as “a modern-day classic.”
Ronald Lewis Sklut was born March 25, 1931, in Morris, Ill., and he later changed his surname. He once told an interviewer that he defied his father’s wishes to become a lawyer.
He graduated in 1953 from Northwestern University in Evanston, Ill., studied at the Sorbonne in Paris and in 1955 received a master’s degree in international relations from Harvard University. He served in the Army and Foreign Service in the 1950s, before deciding he “wasn’t diplomatic enough to be a diplomat.”
He worked as a magazine editor in New York before embarking on a peripatetic career as a visiting scholar at Washington’s Carnegie Endowment for International Peace and Woodrow Wilson International Center for Scholars. After stints at Yale, Princeton, George Washington University and the University of Texas, he became a professor of international relations at the University of Southern California in 1986, but his primary residence remained in Washington.
He never married. Survivors include a brother, Bruce Sklut of Morris.
Mr. Steel’s other books included “Imperialists and Other Heroes” (1971) and “Temptations of a Superpower” (1995), in which he wrote that the United States was “still hobbled by our cold war ways of looking at the world” and that huge military expenditures limited the country’s commercial competitiveness and innovation.
In 2000, Mr. Steel published “In Love With Night: The American Romance With Robert Kennedy,” a clear-eyed, even harsh study of the onetime U.S. attorney general and senator who was assassinated in 1968 while campaigning for president.
Instead of polishing the Camelot legacy of the Kennedy family, Mr. Steel emphasized Robert Kennedy’s work as a legal aide in the 1950s to the reckless anti-communist witch hunter Sen. Joseph R. McCarthy (R-Wis.). He depicted Kennedy as a manipulative, even ruthless political operative who used the levers of government to spy on the Rev. Martin Luther King Jr. and to coordinate assassination attempts of Cuban leader Fidel Castro.
“Although he is remembered to this day as an idealist who brought emotion to politics,” Mr. Steel wrote, “he was also an agile and unsentimental realist in the pursuit and the wielding of political power.”
The book was variously seen as an unsentimental effort to set the record straight about Kennedy — or, from another point of view, to tarnish the memory of an American martyr.
Historian Sean Wilentz wrote in the New York Times Book Review that Mr. Steel sought “to debunk what he calls a liberal myth, the assumption that Robert Kennedy embodied the motivating values of American liberalism and would have pursued them with passionate conviction if he had been elected president.”
Mr. Steel acknowledged that the 1963 assassination of John F. Kennedy had a transformative effect on his younger brother, making Robert Kennedy a more sympathetic, even tragic figure whose potential would forever be unfulfilled.
“Much of Kennedy’s allure,” Mr. Steel wrote, “lies in the future conditional: in what he would have been, what he would have done.”