Disclaimer: No clear chain of command existed at Abu Ghraib because so many individual members of various companies and brigades were thrown together there; the chaos and lack of accountability that ensued created an environment that was ripe for abuse. According to an internal military investigation, overall responsibility for detainee operations never came together under one person short of Lt. Gen. Sanchez himself, who was the chief commander in Iraq. "It is important to understand that the MI units at Abu Ghraib were far from complete units," reads the internal report. "They were small elements from those units. Most of the elements that came to Abu Ghraib came without their normal command structure. The unit Commanders and Senior [Noncommissioned Officers] did not go to Abu Ghraib but stayed with the bulk of their respective units. The bringing together of so many parts of so many units, as well as civilians with very wide backgrounds and experience levels in a two month time period, was a huge challenge from a command and control perspective."
Sources include the Fay Report and the Taguba Report.