The instability caused by a revived insurgency that took over Iraq’s second-largest city of Mosul in June 2014 has facilitated the emergence of new armed actors and deepened the influence of older ones.
The level of security engagement Baghdad receives from the West, including cooperation with the 60-nation coalition against the Islamic State, has not strengthened Prime Minister Haider al-Abadi’s position. His government remains fragile and fragmented, unable to consolidate power and exercise authority over militias that have become necessary in its fight against the Islamic State.
In addition, the prime minister is constrained by the inertia of the political system and the vested interests of powerful actors from his own Shiite sect that are averse to reform. Today, his position grows more uncertain as an intra-Shiite Arab power struggle threatens to upend his tenure.
Source http://www.worldpoliticsreview.com/articles/17403/no-authority-shiite-militarization-in-a-fragmented-iraq