In an appearance on "Fox News Sunday" a few days ago, Mitt Romney was asked whether, given what we know today, the 2003 U.S. invasion of Iraq was the right thing to do. Romney wouldn't say. "Oh boy, that's a big question," Romney answered. "And going back and trying to say, given what we know now, what would we have done? Would we have invaded or not? At the time, we didn't have the knowledge that we have now." Romney mentioned intelligence before the war suggesting that Saddam Hussein had weapons of mass destruction. After the war, U.S. and international...