*ping*
I see it as being almost certainly leaked deliberately, with Rummy's agreement if not actually on his own recognizance.
A few questions:
Where and how would he get information that would allow him to draw these conclusions?
What process led to his writing this memo?
Was he fired or did he resign?
I'm beginning to think he just walked. A possible scenario is him becoming aware that what we were doing wasn't working. But the generals, Joint Chiefs, et al, were continuing to support the Big Military line, the 'Commanders in the Field' were continuing to parrot the words that would ensure the continuance of their careers, every other voice heard by the President was for 'staying the course'. And the President listened to the 'experts', and was loyal to them.
Rummy would not be the first high government official who was a good soldier for his Administration, who was more than ready to speak his own mind after leaving.