The U.S. military presence in Iraq is currently in a transitional phase. Either the anti-U.S. insurgency will be brought under control and security will be provided to those forces involved in nationbuilding; or the insurgency will expand, and U.S. goals in Iraq will be undermined by increasing civil unrest. It is imperative that the former objective be accomplished while the later fate be avoided. To ensure this outcome, U.S. policymakers must understand...