FILE - In this June 17, 1987 file photo, American historian Fritz Richard Stern appears during his speech in Bonn, Germany. Stern, a refugee from Nazi Germany who became a prominent historian and a longtime professor at Columbia University, died Wednesday, May 18, 2016 at his home in New York. He was 90. (AP Photo/Hermann J. Knippertz, File)

NEW YORK - Fritz Stern, a refugee from Nazi Germany who became a prominent historian, government adviser and a longtime professor at Columbia University, has died. He was 90.

Katrin Maria Daehn, a spokeswoman for Stern's German publisher, C.H. Beck, told The Associated Press that Stern died Wednesday at his home in New York City. She had no additional details.

He was born in the former German province of Silesia (now in Poland) to a prominent family that had converted from Judaism to Christianity. But the Sterns felt increasingly menaced by Hitler's reign and left in 1938 for New York, where he received an undergraduate and master's degree and Ph.D. from Columbia. He taught there for more than 40 years, specializing in European history, before retiring in 1997. He also briefly served as provost.

In books, essays, interviews and lectures, he probed the rise of Nazism and the treats to democracy: On occasion, he advised government officials. In the early 1990s, he was among the experts asked to consult with then-British Prime Minister Margaret Thatcher on German reunification, which he supported. In 1993, he took a leave absence from Columbia after being appointed a senior aide to his friend Richard Holbrooke, the U.S. ambassador to Germany.

In a message of condolence Wednesday to Stern's widow, Elisabeth Sifton, German President Joachim Gauck described Stern as "a historian of great erudition and a wise, great person." His survivors include Sifton, his second wife; two children and three stepchildren, among them New York Times editor Sam Sifton.

"Fritz Stern rightly demanded of us Germans that the crimes against the Jews be preserved in our collective memory, to honour the victims, to learn from this rupture of civilization, and to develop standards for shaping the present," Gauck wrote. He added that Stern "served peace by building bridges of understanding between times and people" and pointed to his interest in reconciliation between Germans and Poles.

Sifton, the daughter of theologian Reinhold Neibuhr, has worked as an editor and publisher at Viking Penguin, Alfred A. Knopf and Farrar, Straus & Giroux and is author of "The Serenity Prayer: Faith and Politics in Times of Peace and War."

Stern's books included "The Politics of Cultural Despair," ''The Failure of Illiberalism" and "Five Germanys I Have Known." He also was a frequent commentator on current events. In a 2004 speech, he spoke of parallels between the Nazis and the Christian right. Earlier this year, he told The History News Network that presumptive Republican presidential nominee Donald Trump was a symptom of the "dumbing down of the country."

"When I arrived in this country, Franklin Roosevelt was the president," he said. "That someone like Trump, who is a nobody except for his money, immense ambition and ugliness, is not only offering himself but is actually accepted by many people as a candidate, is simply incomprehensible."

News from © The Associated Press, 2016