Tim O'Brien matriculated at Macalester College. Graduation in 1968 found him with a BA in political science and a draft notice.
O'Brien was against the war but reported for service and was sent to Vietnam with what has been called the "unlucky" Americal division due to its involvement in the My Lai massacre in 1968, an event which figures prominently in In the Lake of the Woods. He was assigned to 3rd Platoon, A Company, 5th Battalion, 46th Infantry, as an infantry foot soldier. O'Brien's tour of duty was 1969-70.
After Vietnam he became a graduate student at Harvard. No doubt he was one of very few Vietnam veterans there at that time, much less Combat Infantry Badge (CIB) holders. Having the opportunity to do an internship at the Washington Post, he eventually left Harvard to become a newspaper reporter. O'Brien's career as a reporter gave way to his fiction writing after publication of his memoir If I Die in a Combat Zone, Box Me Up and Send Me Home.
Tim O'Brien is now a visiting professor and endowed chair at Texas State University - San Marcos (formerly Southwest Texas State University) where he teaches in the Creative Writing Program.