From the Summary: "Operation Iraqi Freedom overthrew Saddam Hussein's regime, but Iraq remains unstable because of Sunni Arab resentment and a related insurgency, compounded by Sunni-Shiite violence that some believe has grown into a civil war. Mounting U.S. casualties and financial costs - without clear signs of security progress - have intensified a debate within the United States over the wisdom of the invasion and whether to wind down U.S. involvement without completely accomplishing initial U.S. goals. U.S. Defense Department reports are expressing more pessimism about security in Iraq and they, as well as Bush Administration officials, are expressing some frustration at the unwillingness of the Iraqi government to disband sectarian militias that are committing violence against civilians of rival sects. U.S. difficulties in Iraq are reflected in reported Administration memos by outgoing Defense Secretary Rumsfeld, National Security Adviser Stephen Hadley, and in the December 6, 2006, report of the Iraq Study Group co-chaired by former Secretary of State James Baker and former House International Relations Committee chair Lee Hamilton. Some in Congress - as well as the Iraq Study Group - believe that major new initiatives are required. The Study Group recommendations focus on intensified regional diplomacy to enlist help from neighboring states to calm their protégé factions in Iraq. Others believe that U.S. counter-insurgent operations are hampered by insufficient U.S. troop levels, but several Members and outside experts maintain that sectarian violence is placing U.S. forces in the middle of civil war and that setting a timetable for withdrawal, or otherwise reducing U.S. support for the Baghdad government, might force compromise among Iraqi factions. Still others maintain that the U.S. approach should focus not on counter-insurgent combat but on reconstruction and policing of towns and cities cleared of insurgents, including neighborhoods of Baghdad."
CRS Report for Congress, RL31339