Secretary of Defense Robert Gates on “the risks of precipitous action”:http://www.pbs.org/kcet/tavissmiley/archive/200903/20090311_gates.html:

I think one of the biggest lessons learned in this is that if you are going to contemplate preempting an attack you had better be very, very confident of the intelligence that you have. And I think that the lessons learned with the failure to find the weapons of mass destruction and some of the other things that happened will make any future president very, very cautious about launching that kind of conflict or relying on intelligence.

He’s going to ask a lot of very hard questions, and I think that hurdle is much higher today than it was six or seven years ago. And my personal view is that any future president, this current president or any future president, while they have to retain [the option], if they have very solid evidence that we are about to be attacked that we be in a position to take action to prevent that.

I think, though, that the area first of all will be are we going to be attacked here at home as one of the thresholds, and then the quality of the intelligence would be another.

Call it the Gates Doctrine.