I don't think Al Qaeda is organised like that, with a central command structure. As I understand it, there's Bin Laden and those around him shaping the ideology, and promoting it - and there are people who like the sound of that ideology and use it as a basis for organising and going out and killing people or whatever, wherever they are, or wherever they can get to. A kind of franchise.

That means it's vastly more difficult to counter than a centrally organised and directed organisation. Wipe out Bin laden and those around him, and there's no reason to think that Al Qaeda would cease to be doing terrible stuff, or even be in any way weakened.

As Obama pointed out in this clip responding to McCain, before the invasion of Iraq, there wasn't any Al Qaeda affiliated activity in Iraq (apart from in a small area up in the North on the border with Iran outside the control of Baghdad). In the chaos after the invasion and the total collapse of civil society it was Liberty Hall for insurgents of all kind, and plenty of scope for people with Al Qaeda sympathies, largely from Saudi Arabia, to start blowing up Americans and Iraqis.