O'Brien was drafted for military service in 1968, two weeks after completing his undergraduate degree at Macalester College in St. Paul, Minnesota, where he had enrolled in 1964. He earned a bachelor's degree in government and politics. An excellent student, O'Brien looked forward to attending graduate school and studying political science. During the course of his college career, O'Brien came to oppose the war, not as a radical activist but as a campaign supporter and volunteer of Eugene McCarthy, a candidate in the 1968 presidential election who was openly against the Vietnam War.
In 1968, the war in Vietnam reached its bloodiest point in terms of American casualties, and the government relied on conscription to recruit more soldiers. Further, graduate school deferments, which exempted students from the draft, were beginning to be discontinued, though O'Brien did not seek out this recourse. Disappointed and worried, O'Brien — like his character "Tim O'Brien" — spent the summer after his graduation working in a meatpacking plant. Unlike his character, however, O'Brien passed his nights pouring out his anxiety and grief onto the typewritten page. He believes it was this experience that sowed the seeds for his later writing career: "I went to my room in the basement and started pounding the typewriter. I did it all summer. My conscience kept telling me not to go, but my whole upbringing told me I had to."
