Bring up Iraq -- and expect to end up in an argument. Conservatives are no different from liberals in rehashing the unpopular war, which has become a sort of whipping boy for all our subsequent problems. The Wall Street Journal columnist Peggy Noonan recently enumerated countless pathologies that followed Iraq. Yet to examine her list is to learn just how misinformed we have become in our anguish over the intervention. Noonan writes of Republicans: "It [Iraq] ruined the party's hard-earned reputation for foreign-affairs probity. They started a war and didn't win it." We can argue over whether the result...