Lawrence Wilkerson (chief of staff to U.S. Secretary of State Colin Powell during the first term of the Bush II administration) has spoken out since 2005 on how Cheney and Rumsfeld subverted the statutory national security decision making process in instigating the 2003 U.S. invasion of Iraq.

Conversations with History - Colonel Lawrence Wilkerson - 03 April 2008.
"Vice President Cheney and America's Response to 911."
Harry Kreisler, Institute of International Studies, University of California at Berkeley.

Evidence that at least the U.S. Army considers the subversion of that process a serious matter (after all, in addition to the millions of Iraqis who have suffered from the ongoing fiasco, so too has the U.S. Army), consider the recent appearance of this Special Edition of Military Review:
"Interagency Reader," [pdf] June 2008.