Henry Graff, a Columbia University professor who studied the past and present as a scholar of the presidency and, as an Army translator during World War II, foreshadowed the future from decrypted Japanese diplomatic messages, died April 7 in a hospital in Greenwich, Connecticut. He was 98.

The cause was complications of the new coronavirus, said Molly Morse, his granddaughter. He lived in Scarsdale, New York.

An author of 12 books and countless articles and a regular contributor to The New York Times Book Review, Graff was best known as a keen observer of the men who occupied the White House — 17 of whom presided during his lifetime.

He knew several personally, including Harry Truman and Gerald Ford, who sat in on his popular seminar at Columbia; and Lyndon Johnson and Bill Clinton, both of whom appointed him to presidential panels.

Playing Boswell to Johnson’s advisers on Vietnam, Graff wrote the book, “The Tuesday Cabinet: Deliberation and Decision on Peace and War Under Lyndon B. Johnson” (1970), which he later described as “an effort at explaining the administration’s Vietnam policy as the president and his chief aides said they understood it.”

While he rhapsodized about teaching at Columbia, which he did from 1946 until he retired in 1991, he exulted in his exploits as an Army translator shortly after Pearl Harbor. He was assigned to the Signal Intelligence Service in Washington, a precursor of the National Security Agency, because he understood Japanese. He had studied the language more or less by chance as a prerequisite to minoring in Asian history during a semester at Columbia when Chinese language courses were not being offered.

In November 1943, he translated part of a message deciphered from Japan’s complex Purple code that had been sent by Hiroshi Oshima, the Japanese ambassador in Berlin, to the foreign office in Tokyo detailing German plans to repel the expected Allied invasion of northern France on D-Day.

Graff quoted General George Marshall as saying “that message was worth 25,000 men’s lives.”

“I, a kid, would come in and look to see if we had any messages from Oshima to the Japanese Foreign Office,” he recalled. “And I was reading messages that reported his conversation with Hitler the day before. I cannot tell you other than I felt that I was at the center of the universe.”

Nine months later, he translated another intercepted message, this one from Japan to the Soviet Union.

“I was the first American, the first member of the Allied side, to know Japan was going to get out of the War,” he said, “because I was working at two in the morning in 1945 shortly after Hiroshima, and I got this message asking Bern, Switzerland, to help get them out of the war.”

Graff was expected to be deployed with Allied invasion forces had Japan not surrendered.

Henry Franklin Graff was born Aug. 11, 1921, in Manhattan to Samuel Graff, a salesman in the Garment District, and Florence (Morris) Graff, both descendants of Jewish immigrants from Germany. His maternal grandmother’s family had a clothing store in East Harlem.

Raised in the Inwood section of Manhattan, he graduated from George Washington High School at 16 and earned his bachelor of social science degree from City College in 1941. He was working toward his master’s at Columbia (“I was the first Jew in the Columbia History Department,” he said) when he enlisted. After the war, he taught history at City College before joining the Columbia faculty in 1946 and earning his doctorate in 1949.

He married Edith Krantz in 1946; she died in 2019. He is survived by their two daughters, Iris Morse and Ellen Graff; five grandchildren; and five great-grandchildren. His twin sister, Myra Balber, died.

Graff wrote “The Modern Researcher” (1957) with historian and cultural critic Jacques Barzun, a colleague at Columbia; and “The Presidents: A Reference History” (1984). He was honored with Columbia’s Great Teacher Award and with its Mark Van Doren Award for Teaching.

Kenneth Jackson, one of his successors as chairman of the history department, said that Graff was that rare Columbia professor who also received an honorary doctorate from the university.

Graff was chairman of the juries for the Pulitzer Prize in American history and the Bancroft Prize in history by Columbia University Libraries. He was appointed by Johnson to the National Historical Publications Commission, and by Clinton to the President John F. Kennedy Assassination Records Review Board.

Graff once said that American scholars of the United States are twice blessed, because the nation is young enough so that its historical record is largely intact, and because historians have the academic freedom to analyze that record critically.

He regarded the presidency as “the litmus paper for testing the nation’s aims and character.”

“When wearing their historical laurels and burdens,” he wrote, “they symbolize even better than the Caesars the fascinating disparity between vast opportunity for personal glory and the uncommonness of the gift to use it wisely.”

But, he added, “in offering themselves for posterity’s judgment, they confront a standard no one has defined.”

This article originally appeared in The New York Times .