Despite his claims of expertise on military affairs, McCain adopted and forcefully advocated on behalf of the bogus vision of military transformation that was pursued by Donald Rumsfeld. This strategy thought high powered precision-guided weaponry could make up for fewer troops. Hence, Rumsfeld advocated for a very small invasion force. Of course the problem with this vision is that it totally ignored the aftermath of any such invasion. As member of the Senate Armed Services Committee, McCain did not oppose Rumsfeld's approach in the fall of 2002. Instead he vigourously advocated on behalf of invading Iraq with few troops.
Despite being in the Vietnam war, McCain did not learn the lesson of the Vietnam war, which is that you cannot win a war from the air. The USSR learned that same lesson in Afghanistan.