Nicholas deB. Katzenbach, who helped shape the political history of the 1960s, facing down segregationists, riding herd on historic civil rights legislation and helping to map Vietnam War strategy as a central player in both the Kennedy and Johnson administrations, died Tuesday night at his home in Skillman, N.J. He was 90.

His death was confirmed by his wife, Lydia.

Mr. Katzenbach was one of the “best and the brightest,” David Halberstam’s term for the likes of Robert S. McNamara, McGeorge Bundy, Walt Rostow and other ambitious, cerebral and often idealistic postwar policy makers who came to Washington from business and academia carrying golden credentials. Mr. Katzenbach, an attorney general under President Lyndon B. Johnson, was the son of a New Jersey state attorney general, a Rhodes scholar, a war hero and a law professor at Yale and the University of Chicago....