He already he got his jollies on 9/11, with the most audacious and stunning surprise attack in human history. The deterrent part is just about getting away with it. There's nothing very complicated or mysterious about it.
I think history will show that the Japanese attack on Pearl Harbor did much more damage to our primary tool for fighting a war. Our military force. The Tet offensive was also fairly effective and was directly against our military forces. Its true that the attack on the World Trade Center was more horrific and more devious due to the surprise attack on civilians, but look at what the US militray force still has available to fight with. Saddams attacks were the kind that one would expect from a future thinking enemy that was fighting a very long war. Not the kind of attack someone living on the borrowed time of a cease fire agreement should have undertaken. So in an attempt to get his jollies off, he has succeded in the destruction of the Taliban, the all out war against Al Queda and his eventual complete and utter demise. I guess its possible that he is that stupid.
The deterrent part is just about getting away with it.
Where is he going ? He is trapped inside a bunker surrounded by enemies.