A native of New York City, Bryan attended the Hotchkiss School in the class of 1954, and earned a Bachelor of Arts at Yale University in 1958.
His parents were Joseph Bryan, III and Katharine Barnes Bryan; after they divorced his mother married author John O'Hara.He served in the U.S. Army in South Korea (1958–1960), but not happily. He was mobilized again (1961–1962) for the Berlin Crisis of 1961.
He was an intelligence officer. He was editor of the satirical Monocle (magazine) (from 1961), Colorado State University writer-in-residence (winter 1967), visiting lecturer University of Iowa writers workshop (1967–1969), special editorial consultant at Yale (1970), visiting professor University of Wyoming (1975), adjunct professor Columbia University (1976), fiction director at the New York City Writers Community from (1977), lecturer in English University of Virginia (spring 1983), and Bard Center fellow Bard College (spring 1984). His first novel won the Harper Prize (1965). Bryan is best known for his non-fiction book Friendly Fire (1976).
It began as an idea he sold to William Shawn for an article in The New Yorker, then grew into a series of articles, and then a book. It describes an Iowa farm family, Gene and Peg Mullen, and their reaction and change of heart after their son's accidental death by friendly fire in the Vietnam War. It was made into a 1979 television movie of the same name, for which he shared a Peabody Award. It's also been cited in professional military studies. Bryan died from cancer on December 15, 2009 at his home in Guilford, Connecticut