When America entered it in 1917, the Great War was just that—an immense and ennobling effort we were making on behalf of all mankind. Ten years later it was the murderous scam of munitions brokers and Wall Street—a message that seeped deep enough to persuade the nation that Hitler didn’t pose a real threat. Now a new wave of revisionism is rolling over Europe, and John Lukacs thinks it’s on its way here. In an important essay, he traces the course of its predecessors and tells why this one might be especially dangerous.