Fionn, you are right that this definitional issue isn't new, and that the semantic distinctions have been important in a number of other conflicts for a variety of reasons. In fact, we in the US have gotten used to our wars being called something else (I believe Korea was a "police action," and Vietnam was a "conflict"), while non-wars are called wars (the "war on poverty," the "war on hunger," the "war on drugs," etc.). Probably none of these words is a perfect fit, because all are defined to some extent by precedent, and this situation departs from many of the established precedents.

Still, for what it's worth, I think "war" is the right word to use. We have an identified foreign enemy that is inextricably linked to (and supported by) a foreign government. That enemy attacked us on a scale that is not typical of any of the usual "crimes" we are familiar with -- as much as smaller-scale acts of terrorism have become a distressing fact of life in many countries, I know of no other example in world history where over 5,000 people were intentionally killed in the course of a single hour and it was NOT considered an act of war. We are responding with the tools of war: armed forces, high-stakes diplomacy, international alliances, a high-tech economic blockade, dramatically increased home-front security measures, etc. True, we might employ some of these tools in a more traditional crime-fighting context, but when they are used together, on this scale, it sure looks like war to most of us. You know the saying: if it looks like a duck and quacks like a duck, it's probably a duck. Well, what does this look like to you?

And as much as some have tried to couch our aims in more limited terms, it is becoming increasingly clear that our objective is the destruction of our enemy. That doesn't necessarily mean that we'll kill them all -- hell, even at the end of World War II (I trust that we can agree THAT was a war), we imprisoned some of the senior Nazis rather than executing them en masse, and left the Emperor of Japan on his throne. But it does mean that we are using the tools of war in order to achieve more-or-less traditional war aims. Given that our enemy is not only al Qaeda, but also the Taliban, I think it is fair to say that we are seeking to destroy the Taliban, and allow it to be replaced by another government (at some point they may sue for peace and we may consider modifying our goals, but for the time being we're out to get them). The destruction of a foreign government is also something that most people would associate with war, rather than with law enforcement.

Most importantly, though, we need to call this a war because we need to make sure that people all over the world recognize it as a war. We're not in Afghanistan to arrest a bank robber, or even a murderer; we're there to kill people and break things until the existing (although unrecognized) government either surrenders or collapses, after which we can have a free hand to dismantle/destroy the offensive force that was employed against us. It is likely to result in some additional actions against us, by a foreign military force, using both conventional and unconventional means. And it will require sacrifice, and resolve. The word "war" lays the foundation for that better than any other term I've heard used. It's an ugly word, but then it's an ugly situation: I still prefer to call it what it is.