Very recent history, but a good read, in this new product from RAND:

Developing Iraq’s Security Sector: The CPA’s Experience
Soon after the coalition’s occupation of Iraq began in April 2003, it became evident that prewar assumptions about the security situation that would follow the ouster of Saddam Hussein had been unduly optimistic. The environment was not benign—in fact, it was deteriorating. Iraqi security forces had largely disintegrated, and those that remained were incapable of responding to rising criminality and political violence. In this environment, the coalition confronted three security imperatives: (1) to restore order and neutralize insurgents and terrorists; (2) to rebuild Iraqi security forces, which could eventually take on responsibility for Iraq’s security; and (3) to build security sector institutions, such as national security management institutions, the interior and defense ministries, and the justice sector, to ensure that the Iraqi security sector could be an effective bulwark for a democratic Iraq in the future.

At the time that the Coalition Provisional Authority (CPA) handed over authority to the Iraqi Interim Government (IIG) on June 28, 2004, it was clear that the coalition had made little progress in the first task. Insurgent and terrorist violence was escalating, organized crime was flourishing, and the security situation was threatening both the political transition and the reconstruction program. The coalition’s record on the second and third tasks, however, is somewhat less simply categorized. From April 2003, the coalition embarked on efforts to rapidly field Iraqi security forces and to build security sector institutions. This effort was broad in scope, but its implementation was patchy, its results were varying, and its ultimate success or failure remains difficult to determine.

Significant analysis has focused on the inability of the coalition to adequately counter political violence and crime in post-Saddam Iraq. There has also been considerable discussion about the coalition’s effort to develop Iraqi security forces. The matter of institutionbuilding, however, has been largely ignored by observers and policymakers; it is often seen as a long-term issue that is too far removed from immediate security needs. But the three efforts are interdependent: Iraq’s future security depends on its indigenous security forces, and these forces’ success and sustainability depend on the institutions that support them. This report concerns itself with the efforts to build both forces and institutions in Iraq. It provides a historical record of the coalition’s experience and seeks, insofar as is possible at this early stage, to draw lessons from the successes and failures of that experience.