Of course the whole “preemption” debate has not been helped by neoconservative insistence on using the word “preemption” to mean what international relations people have typically called “prevention.” A primer.
A preemptive war is a war where you fire the first shot because you know the other guy is about to shoot and you’ll gain a tactical advantage by striking first. The classic example is the 1967 Israeli-Arab war. Israel knew that Egypt and Syria were gearing up for an attack. Because Israel is smaller (and was especially small back then) both in land mass and in population than its adversaries, the Arabs had a kind of general strategic advantage. In order to counter the manpower of the Egyptian standing army, Israel needed to mobilize a large number of reservists, such a large number that keeping them mobilized for a sustained period of time would destroy the Israeli economy. Hence, Egypt could gear up for war and then just sit around until Israel was forced to demobilize and then attack at its leisure while Israeli forces were unprepared. Israel’s advantage, conversely, was that it had a better-trained, better-equipped, and basically better military. So they struck to preempt the coming Egyptian attack, thus gaining tactical advantage and winning the war. From the Israeli point of view, a smart move, just the sort of thing bright leaders would do.
A preventative war is a very different bag of worms. Here the idea is that you’re Country X and you foresee conflict with Country Y coming down the pike at some point. Right now, X is stronger than Y, but the trends suggest that Y is getting stronger. Under the circumstances, you prefer war now, when Y is weak, to the possibility of war later, when Y will be stronger. General Patton, I believe, wanted to wage a preventative war of this sort with the Soviet Union in 1945 or 1946 on the theory that “whatever happens we have got / the atom bomb and they have not” which would be preferable to waiting for Stalin to reconstruct his country, build a bomb, and then have us fight a big war later on. He didn’t want to preempt anything in particular, it was just a general sense that we should strike during our moment of maximum strength. General MacArthur had a similar view of the state of play vis-à-vis Red China during the Korean War. Mao’s regime was, relatively speaking, weak and also hostile. So while Truman wanted to avoid a wider war on the theory that big wars are bad, MacArthur welcomed it on the theory that war was inevitable and we might as well get it done with before China got stronger.
Neither of those things happened, and the “wait and see” camp was, in both cases, ultimately proven correct in its estimation that war could be avoided in a manner consistent with American security in the long run.
One preventative war that did happen was world war one. The feeling in the German national security community was that Russia was a rising power and that Russo-German conflict was inevitable. Hence, if a good pretext for going to war with Russia could be found, it should be taken. So when Austria became embroiled in a conflict with Serbia, the German government did something unusual. Normally a great power would take diplomatic action to avoid getting dragged into a big war by a weaker ally (see Truman’s behavior in Korea). Germany, however, wanted a war, and so its diplomats encouraged Austria to take a hard line in hopes of provoking a wider fight. They got the fight they wanted, and things didn’t turn out so well in the end.
Long story short, preventative war does not have a very good record, and its reverse has a pretty good one. What the Bush national security strategy is really arguing for is preventative war, fighting Iraq not because it’s a threat, but because it wasn’t a threat, but might have become one some day. I don’t have a huge problem with that idea, but it’s the sort of thing that ought to be done properly, in a way that strengthens rather than weakens our alliances, and that’s only done when there aren’t more pressing objectives, like beating al-Qaeda and dealing with North Korea.