The Pentagon has released it's congressionally mandated quarterly report on the progress of security operations in Iraq.
Titled Measuring Stability and Security in Iraq -- March 2007 (47-page pdf), the report details the shortcomings of the U.S.-created Iraqi armed forces as well as the failure of the Iraqi government to transcend the formidable sectarian rivalries that are tearing the country apart.
Since the last report, a series of high-casualty and high-profile attacks primarily against Shi'a civilians—likely perpetrated by AQI (Al Qaeda in Iraq)— have hampered efforts to demobilize militia groups and have set back the reconciliation process. Likewise, some Shi'a extremist groups have used "death squads" to kill and intimidate Sunni civilians. This type of sectarian violence in Baghdad and the failure to reliably apprehend and punish criminals and terrorists has hampered progress toward reconciliation. ...
The conflict in Iraq has changed from a predominantly Sunni-led insurgency against foreign occupation to a struggle for the division of political and economic influence among sectarian groups and organized criminal activity. As described in the January 2007 National Intelligence Estimate, the term "civil war" does not adequately capture the complexity of the conflict in Iraq, which includes extensive Shi'a-on-Shi'a violence, al-Qaida and Sunni insurgent attacks on Coalition forces, and widespread criminally motivated violence. Some elements of the situation in Iraq are properly descriptive of a "civil war," including the hardening of ethno-sectarian identities and mobilization, the changing character of the violence, and population displacements. Illegally armed groups are engaged in a self-sustaining cycle of sectarian and politically motivated violence, using tactics that include indiscriminate bombing, murder, and indirect fire to intimidate people and stoke sectarian conflict. Much of the present violence is focused on local issues, such as sectarian, political, and economic control of Baghdad; Kurdish, Arab, and Turkomen aspirations for Kirkuk; and the political and economic control of Shi'a regions in the south. Although most attacks continue to be directed against Coalition forces, Iraqi civilians suffer the vast majority of casualties. Given the concentration of political power and population in Baghdad and the city's ethnic and sectarian diversity, Baghdad security remains the key to stability in Iraq. ...
The level of violence in Iraq continued to rise during this reporting period as ethnic, tribal, sectarian, and political factions seek power over political and economic resources. Consistent with previous reports, more than 80% of the violence in Iraq is limited to four provinces centered around Baghdad, although it also exists in other population centers, such as Kirkuk, Mosul, and Basrah. Sectarian violence and insurgent attacks still involve a very small portion of the population, but public perception of violence is a significant factor in preventing reconciliation on key issues. The conflict in Iraq remains a mosaic and requires maximum flexibility on the part of the Coalition and the GOI to uproot the main drivers of violence in different areas of the country.
Aside from the analysis of the overall political and military picture, the report goes into great detail (not Order of Battle specific, but good) about the Iraqi security forces -- down to the training and materiel that various services and units within those services have received.
The report portrays a scenario in which U.S. forces will be needed for the foreseeable future.