Really long, detailed story in the New Yorker, again from Seymour Hersh, about a clandestine project called Copper Green. Originally an interrogation program designed to operate outside of the Geneva Convention at Guantanomo, it was imported to Iraq under orders from Rumsfeld.
http://newyorker.com/fact/content/?040524fa_fact
Geoffrey Miller was sent in from Guantanamo to "gitmoize" the Iraq operation, and it was his arrival that is timed with the start of the Iraq abuses.
It's all pretty shocking, and the story shatters the administration's position that a small group of soldiers acting alone were responsible for the abuses.
It's a very long read, (literally! why are the columns so narrow?) but it's definitely worth your time.