The phenomenon of Iraq's Shia warlords and the militias they lead has significant implications for the conduct of the war against Islamic State in Iraq and Syria (ISIS), including for U.S. policy interests and for U.S. Landpower forces deployed in-country. In this monograph, Dr. Norman Cigar analyzes the rapid resurgence of the Shia militias and the warlords thanks to a mass popular mobilization in response to the severe ISIS threat to the country in 2014. The militias have played a key role in helping to stabilize the situation on the ground, while the Iraqi Army has been rebuilding with the help of the international Coalition. At the same time, the warlords have become significant political players who have an impact on issues of interest to the United States, such as sectarian reconciliation and the formation of a National Guard in Sunni areas, which have implications for the future of Iraq's security and stability.