Iran's influence over the post-Saddam government in Iraq is substantial because the predominant parties in that government have long enjoyed Tehran's sponsorship. An emerging concern is that Iran's influence has extended to support for militant groups in Iraq. U.S. officials say that sophisticated explosive devices are entering Iraq from Iran, suggesting that Iran, or factions within Iran, are backing Iraqi factions that use violence to oppose the U.S. presence in Iraq.

The following casualty data was compiled by the Department of Defense (DOD), as tallied from the agency's press releases. Included are statistics on fatalities during Operation Iraqi Freedom, which began on March 19, 2003, and is ongoing, as well as on the number of fatalities since May 1, 2003, plus statistics on those wounded, but not killed, since March 19, 2003. Statistics may be revised as circumstances are investigated and as all records are processed through the U.S. military's casualty system.

Operation Iraqi Freedom succeeded in overthrowing Saddam Hussein, but Iraq remains unstable because of Sunni Arab resentment and a related insurgency, compounded by burgeoning sectarian violence. According to its November 30, 2005, “Strategy for Victory,” the Bush Administration indicates that U.S. forces will remain in Iraq until the country is able to provide for its own security and does not serve as a host for radical Islamic terrorists. This report discusses the background of the issue and examines several security challenges, response, and other policy options for the U.S.