The title is a quote from a jubilant Churchill after hearing that the U.S. was joining WWII after Pearl Harbor. Many thought Churchill was being over-the-top, after all, it was 1941; Germany had conquered almost all of continental Europe and was at the gates of Moscow, and the Japanese had taken much of China and were about to go on a rampage throughout the Pacific. But the quote was correct; the size and strength of the United States virtually assured an Allied victory. It would have taken ineptitude of the first-order (or a Nazi nuclear bomb) for us to have lost WWII; our strength in men and material dwarfed that of the Axis powers. The only way we could have lost is if we beat ourselves.
Unfortunately we have something of a history of doing so. Obviously we had to beat ourselves in the Civil War (by definition). And more recently we defeated ourselves in Vietnam. It is the conventional wisdom that the Vietnam War was fundamentally unwinnable, at least politically. I've always believed that the political limitations placed on our forces caused our defeat. Not entirely true, according to an article in NRO today. In it, the author argues that in the period 1968-72 we switched tactics and virtually defeated North Vietnam, and if we had continued to help them they might be in the same position as South Korea, prosperous and free. But what we won on the battlefield we gave up on the negotiating table.
Recently many have compared our current situation in Iraq to Vietnam (including a certain senator from Taxachusetts with a propensity for missing bridges, ahem). This is perhaps not that far from the truth. In Vietnam we won militarily but lost politically. We are in danger of the same in Iraq, if we persist in making foreign policy a bitterly partisan issue. We are the only ones who can defeat us. That is the political lesson of Vietnam. Let's not do it again; let's keep Vietnam as the only mark on our otherwise perfect record in war. Recent polls show a drop in support for the war. Our ultimate victory cannot be in question, it merely requires us to stay the course.
Militarily, it is clear that we've learned the lesson of Vietnam. We aren't suffering large numbers of casualties; we've figured out how to use our superior technology to our advantage. We are much more powerful than any of our enemies. For us to win, all we have to do properly apply our power; which is, of course, more difficult than it sounds.