The perspective that was changed was that we had thought we had the luxury of waiting for the other guy to take the first punch. It cost us 3,000 people and a chunk of Manhattan. And if you look at the Cole and other attacks, this wasn't even the first punch.

There are nations that are dangerous to us. They include Iran, North Korea, and maybe some others. A couple of years ago, they also included Afghanistan and Iraq. The last two are now off the list, and the fact that the list is shorter can't be seen as anything but good news.

The change of perspective meant that it was no longer acceptable to wait for them to do something awful before we did anything ourselves, and we started taking a much closer look at these nations. You can make reasonable arguments that the shift to preemption is not a good shift, but you can't pretend that 9/11 wasn't a viable justification for such a shift.

You can also make reasonable arguments that maybe somebody else should have been targeted first after Afghanistan, like North Korea. There are also good arguments why you get the most benefits by doing Iraq first. But that doesn't change the basic principle. Greedo doesn't get to shoot first any more.