Conspiracy Theorists #1's response:
To facilitate another "galvanizing Pearl Harbor event." And, I'm talking about a big "event." [BTW, I searched PNAC's website, it appears they have redacted the Pearl Harbor reference] It's a helluva lot easier to slip a dirty bomb, or even a nuc, in a place if your the one guarding the door.
But I think the strategy is not so much to lead us into another military adventure, which I am sure that will follow; but rather to lead to the establishment of an open police state, i.e., dictatorship.