On Fresh Air today, Terry Gross talked with New York Times reporter David Kirkpatrick, who has been writing a series of biographical profiles of Senator McCain.
The whole hour is devoted to their discussion and they cover a lot of interesting ground. Mr. Kirkpatrick describes the often bitter feelings of the POWs —not just Mr. McCain— about the Johnson administration’s conduct of the war. They have this exchange:

TG: You say that another conclusion he reached after Vietnam was that you need military power to set the stage for negotiations. Would you talk about that?

DK: Senator McCain comes from a long line of military officers. Members of his family have fought in every American war since 1776.

So the use of force and questions about the use of force come naturally to him – I think more naturally than questions about diplomacy.

So what he took away from Vietnam, in addition to that, was when the Johnson administration called off the bombing as a gesture of good faith to try to negotiate with the North Vietnamese, it emboldened the North Vietnamese and negotiations dragged on.

When the Nixon administration redoubled the bombing, the North Vietnamese came to the bargaining table and that ended the war.

So, for him, use of force is the way to put some muscle into your negotiating power, and diplomacy , without force, is next to useless.

The whole conversation is worth a listen.