Last weekend was full of commentary on September 11. All of it that I saw missed the point. Most of it even managed to keep from mentioning why the attacks happened. Osama bin Lauden and al Queda struck at the US because of two wide-spread beliefs:
The first was that the US was a hollow superpower which would collapse if hit hard enough. They based this on the collapse from within of the USSR. The hope was that a US collapse would create a power vacuum which could be filled by a new Caliphate.
The second belief was that, even if the US did not fall, we did not have the will to engage in a long struggle with significant casualties. The most we were willing to commit to was a risk-free high-altitude bombing or an invasion that only lasted a few days and used overwhelming force. This was based on Viet Nam and our behavior in other conflicts afterward. They also counted in the invasion of Afghanistan by the USSR.
Obviously the first belief was wrong. September 11 was a sting rather than a blow. Instead of collapsing the US, it roused us.
The second belief is more problematic. Had Kerry won in 2004 we would almost certainly have left Iraq and convinced future enemies of our weakness. We may yet snatch defeat from the jaws of victory in Iraq and Afghanistan but we have shown that we are willing to wage a decade-long battle and that we are remorseless about hunting down our enemies.
So, 9/11 happened because of our perceived weakness and as a result we discovered that we are strong, after all.