"But one thing that we have done in the last four years is we have really put pressure on the leadership of this organization [Al Qaeda]. We have killed a significant number of leaders. We've captured others. Those that remain have to look over their shoulders, they have to be on the run. So that even if we don't manage to kill or capture them all within four years, what we do do is put the kind of pressure on them that makes them focus on their own skins, as opposed to carrying out attacks."