...what does Richard Clarke mean when he says: "Iraq is not just a training ground, it's a motivator."?
Did he come out and fully explain this talking point, or better yet was he allowed to expound on the talking point?
It is quite clear to me when we examine the Bush strategy of post invasion occupation of Iraq, there has never been a deliberate intention or post war occupation plan to root out terrorists. The intent I believe all along was to invade Iraq, pull down the Saddam regime, occupy the country, establish permanent military bases (14 to 17) there, install a puppet government and draw on Iraq's vast oil reserves as a steady and consistent supply of oil to the West. For the Bush administration to have assumed that there would be no resistance to these actions either by Iraqis or neighboring countries like Iran, Syria or Jordan, would have been naive or simply foolish thinking at the very best. The minds in this administration I think know better than this, so they did it to stimulate or as Clarke has suggested motivate resistance, which against a technologically superior military force such as the U.S. has, really would come in the form of terrorist style attacks.
I found this animated map on Coalition Fatalities By Location Across Time site very interesting as nearly 99% of the casualties have been incurred along the interior of Iraq and not around the borders where so called insurgents are freely allowed to enter almost the complete perimeter of the Iraqi frontier:
http://www.obleek.com/iraq/index.html