The Post

In 1966 Vietnam, State Department military analyst Daniel Ellsberg accompanies U.S. troops in combat, documenting the progress of U.S. military activities in the region for Secretary of Defense Robert McNamara. On the return flight home, McNamara expresses to Ellsberg and William Macomber his view that the war in Vietnam is hopeless, yet, upon landing, McNamara expresses to the press his confidence in the war effort. Ellsberg overhears this, and becomes disillusioned. Years later, now working for the RAND Corporation, a civilian military contractor, Ellsberg surreptitiously photocopies classified reports documenting the country's decades-long involvement in the conflict in Vietnam, dating back to the Truman administration. Ellsberg then leaks these documents to reporters at The New York Times. Read more on Wikipedia.