3. Depends (the classic answer) on the intel. If we had accurate info on WMD in Iraq in 2002 would we have gone to war? If we had accurate intel on Saddam's intentions prior to his 1990 invasion of Kuwait, could we have prevented it?

This leads to #1:

As a Lieutenant (back in the dark ages) I was a strat intel officer assigned to the Pentagon. We analyzed all kinds of info (political, economic, military, and informational - the classic instruments of power) from all sources for the decisionmaking political and administrative leadership. Responding to our analysis (I'm talking here about the entire intel community) they would use this as input to their policy decisions. Intelligence, of course, was not their only source of critical info. For non-denied areas, the media was often better informed than the entire intel community. This remains the case although, perhaps, the degree to which it is true may have changed. In addition to intel on friends and adversaries the decisionmakers have to take account of our own capabilities. For the military, this is coordinated through the 3 shop. As Graham Allison points out in Essence of Decision (if you haven't read it for pol sci you must ) Presidents are limited by the capabilities of their bureaucracies. Finally, recognize the wisdom of Clausewitz' (Saint Carl to the denisons of SWJ) in his one point of total consistency through all 8 books, that war is the continuation of policy/politics with the addition of other means.

I'll leave the other questions for others more current like Wilf.

Hope this was of some use.

Cheers

JohnT