To the Republicans, that would be the Cold War. But, a better question, what set the conditions that allowed Nazism and Communism to take hold? War, of course. War has also, historically, be the most efficient means of gathering slaves. And of course slavery disappeared from most of the world without war. Moreover, the freeing of the slaves in the Confederacy by the Emmancipation Proclamation was a political move, and hense, accidental to war. The Union did not attack the Confederacy to free to the slaves, so I would not consider it accurate to say that war as an entity "solved" slavery. While one of course cannot deny that there has been some good from wars, how does finding the occasional good compare with all the bad? And how often is it that we must fight one war just to correct the mistakes of past wars?
You're right, of course. I didn't mean to endorse a simple apology for war. But I did find it useful in at least provoking a bit of thought among the knee-jerk anti-war crowd: sometimes you have to go to war. I know that in the country at large, that's not a point that needs to be made and in the context of the larger discussion about war, it's a stupid thing to say--but in my neighborhood, it's just what some people need to hear.
As for the Cold War, that was my guess too, but this car also had libertarian and gay pride stickers on it so I wasn't quite ready to just put it in the loony right bin.