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 on April 7 in a hospital in Greenwich, Conn. He was 98.

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

An author of 12 books and countless articles and a regular contributor to The New York Times Book Review, Professor 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 S. Truman and Gerald R. Ford, who sat in on his popular seminar at Columbia; and Lyndon B. Johnson and Bill Clinton, both of whom appointed him to presidential panels.