From the Summary: "The Obama Administration is facing a security environment in Iraq vastly improved over that which prevailed during 2005-2007. The 'turnaround' has been widely attributed to the 'troop surge' announced by President Bush on January 10, 2007 ('New Way Forward'). Recent Defense Department reports assess that overall frequency of violence is down to levels not seen since 2003, yet insurgents are still able to conduct high profile attacks in several major cities. These attacks have not caused a modification of the February 27, 2009, announcement by President Obama that all U.S. combat brigades would be withdrawn by August 31, 2010, leaving a residual presence of 35,000 -- 50,000 U.S. trainers, advisers, and mentors, with these to be withdrawn by the end of 2011. […] However, some believe that insurgents will take advantage of the drawdown and that a U.S. military presence might be needed beyond 2011 to ensure further political progress and produce a unified, democratic Iraq that can govern and defend itself and is an ally in the war on terror. […]. Mounting U.S. casualties and financial costs--without clear movement toward national political reconciliation-- stimulated debate within the 110th Congress over whether a stable Iraq could ever be achieved, and at what cost. With an apparent consensus within the Administration to wind down the U.S. combat in Iraq, U.S. economic and security aid to Iraq is being reduced."
CRS Report for Congress, RL31339