Sometime in May 2003, shortly after U.S. forces had taken Baghdad and President Bush landed on an aircraft carrier under the banner "Mission Accomplished," an old friend remarked that he thought the war was going pretty well so far. I shook my head and said I thought we were in for trouble.

I bet him that day that Iraq would be a mess in five years' time, a mess being defined as "you'll know it when you see it." I mentioned this bet to Bret Stephens three years later. He'd reviewed my book, "America at the Crossroads" in this...