My impression during my three Arclight tours was that our leaders had no idea of how to win the thing, or end it, just a determination not to be the ones stuck carrying the can when we lost.
Curtis LeMay's "bomb 'em back to the stone age" tactic did work, once it was tried, but by then all we wanted was an opportunity to quit, which North Vietnam 'graciously' allowed us. They then more-or-less instantly occupied the eastern borders of Laos and Cambodia in preparation for their eventual takeover of the south.