"Operation Iraqi Freedom overthrew Saddam Hussein's regime, but during 2004- 2007 much of Iraq was highly violent because of Sunni Arab resentment and a related insurgency, resulting Sunni-Shiite sectarian violence, competition among Shiite groups, and the failure of Iraq's government to equitably administer justice or deliver services. U.S. casualties and financial costs […] stimulated debate within the United States over whether the initial goals of the intervention […] could be achieved, and at what cost. The Administration is now claiming success in reversing the deterioration in security that became acute by the end of 2006, attributing the gains to a 'troop surge' strategy […]. […]. Critics say that the strategy has not, to date, accomplished its primary intent […] and that any security gains are therefore tenuous. […]. The Administration believes that the current U.S. strategy, if continued with only modest reduction in U.S. forces and continued building of Iraq's security forces, is likely to produce a central government able to defend itself. However, some in Congress believe that any progress is likely to unravel without unsustainably high levels of U.S. forces, and that the United States should begin winding down U.S. combat involvement in Iraq, whether or not a unified central government is fully stabilized. Partly because there is a perception that the troop surge is succeeding, there has not been the required level of support in Congress to mandate a troop withdrawal, a timetable for withdrawal, or a significant change in U.S. strategy."
CRS Report for Congress, RL31339