John McCain said the mistake in Vietnam was that the U.S. didn't go all out, invading and bombing north Vietnam. Historians say that could have lead to massive casualties and war with China's huge army.
A fellow Vietnam POW said McCain's an unstable hot head:
McCain has also said (joked?) he wants to bomb bomb bomb, bomb bomb Iran:
McCain's VP choice Sarah Palin, an old heartbeat from the Presidency, implied the U.S. should go to war with Russia over tiny South Ossetia:
All of this has lead many to fear a McCain/Palin armageddon. But so far Obama has shied away from calls for tough ads on the issue. Here's the famous one that worked for Lyndon Johnson during the Vietnam War: