The Pentagon Papers, published 30 years ago this month, proved that the government had long lied to the country. Indeed, the papers revealed a policy of concealment and quite deliberate deception from the Truman administration onward.
A generation of presidents, believing that the course they were following was in the best interests of the country, nevertheless chose to conceal from Congress and the public what the real policy was, what alternatives were being pressed on them from within the government, and the pessimistic predictions they were receiving about the prospects of their chosen course.
Why the lies and concealment? And why, starting in 1969, did I risk prison to reveal the documentary record? I can give a definite answer to the second question: I believed that the pattern of secret threats and escalation needed to be exposed because it was being repeated under a new president.
About the first question, I can still only speculate. Let me speak to the Johnson administration, in which I was a minor participant. The familiar answer is that in 1965, Lyndon Johnson was protecting his Great Society programs by concealing the scale of the war he was launching.