The cause was congestive heart failure, said his son, Paul Lukacs.

An old-fashioned man with a prominent forehead, cosmopolitan accent, and erudite but personal prose style, Dr. Lukacs was a maverick among historians. In a profession in which liberals were a clear majority, he was sharply critical of the left and of the cultural revolution of the 1960s.

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But neither was he satisfied with the modern conservative movement, opposing the Iraq War, mocking hydrogen bomb developer Edward Teller as the “Zsa Zsa Gabor of physics” and disliking the “puerile” tradition, apparently started by Ronald Reagan, of presidents returning military salutes.

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“John Lukacs is well known not so much for speaking truth to power as speaking truth to audiences he senses have settled into safe and unexamined opinions,” John Willson, a professor emeritus of history at Hillsdale College in Michigan, wrote in the American Conservative in 2013. “This has earned him, among friends and critics alike, a somewhat curmudgeonly reputation.”

Dr. Lukacs completed more than 30 books, on far-ranging topics including his native country, 20th-century American history and the meaning of history. His books include “Five Days in London” (1999), the memoir “Confessions of an Original Sinner” (1990) and “Historical Consciousness” (1968), in which he contended that the best way to study any subject, whether science or politics, was through its history.

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He considered himself a “reactionary,” a mourner for the “civilization and culture of the past 500 years, European and Western.” He saw decline in the worship of technological progress, the elevation of science to religion and the rise of materialism.

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He belonged to few academic or political organizations and was unafraid to challenge his peers, whether Arthur M. Schlesinger Jr., Hannah Arendt or British historian David Irving. In “The Hitler of History,” published in 1997, Dr. Lukacs alleged that Irving was sympathetic to the Nazis, leading to threats of legal action from Irving and the removal of passages from the book in England. In recent years, Irving has been widely condemned because of his ties to Holocaust deniers.

Hitler and Stalin were Dr. Lukacs’s prime villains, Churchill his hero. Dr. Lukacs wrote several short works on Churchill’s leadership during World War II. He noted that instead of having a unified country behind him, Churchill had to fight members of his own cabinet who wanted to make peace with the Nazis.

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“If at that time a British government had signaled as much as a cautious inclination to explore a negotiation with Hitler . . . that would have been the first step onto a Slippery Slope from which there could be no retreat,” Dr. Lukacs wrote in “Churchill: Visionary. Statesman. Historian,” published in 2002. “But Churchill did not let go; and he had his way.”

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One book on Churchill attained unexpected popularity after the Sept. 11, 2001, terrorist attacks. Rudolph W. Giuliani, then New York City’s mayor, said he had been reading Dr. Lukacs’s “Five Days in London” and likened New Yorkers to the citizens of London.

The book jumped into the top 100 on Amazon’s bestseller list. (Amazon chief executive Jeff Bezos owns The Washington Post.) But Dr. Lukacs rejected comparisons between London in 1940 and New York City in 2001.

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“The situation was totally different,” he told the Philadelphia Inquirer at the time. “As a matter of fact, it was much worse in England.”

More recently, “Five Days in London” was widely cited as a source for “Darkest Hour,” the 2017 film starring Gary Oldman in an Oscar-winning performance as Churchill.

Janos Adalbert Lukacs was born in Budapest on Jan. 31, 1924. His father, a physician, was Catholic, and his mother was Jewish. Although Dr. Lukacs was a practicing Catholic for much of his life, the Nazis, who occupied Hungary in 1944, considered him Jewish and sent him to a labor camp. He never saw his parents again after the war, his son said.

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By the end of 1944, Dr. Lukacs was a deserter from the Hungarian army labor battalion, hiding in a cellar, awaiting liberation by Russian troops. In 1946, the year he was awarded a doctoral degree in history from a university in Budapest, he arrived by ship in Portland, Maine, his youthful affinity for communism shattered.

Dr. Lukacs was a visiting professor at Princeton University and Columbia University but spent much of his career at Chestnut Hill College, a Catholic school (for women until 2003) in Philadelphia where he taught from 1946 to 1994.

His first wife, the former Helen Schofield, died in 1971 after nearly two decades of marriage. In 1974, he married Stephanie Harvey; she died in 2003. His third marriage, to Pamela Hall, ended in divorce.

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Survivors include two children from his first marriage, Paul Lukacs of Baltimore and Annemarie Cochrane of Elverson, Pa.; three stepchildren from his second marriage, Peter Segal of Charlestown, Pa., Hilary Felton of Royersford, Pa., and Charles Segal of Phoenixville; five grandchildren; and four great-grandchildren. Another stepson, Hugh Segal, predeceased him.

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Dr. Lukacs was a pessimist yet often expressed personal contentment. He wrote warmly about the “pleasure of fresh mornings, driving alone on country roads, smoking my matutinal cigar, mentally planning the contents of my coming lecture whose sequence and organization are falling wonderfully into place, crystallizing in sparks of sunlight.”

“Because of the goodness of God,” he concluded in his memoir, “I have had a happy unhappy life, which is preferable to an unhappy happy one.”