ISIS would be able to recruit Sunni fighters by exploiting the Sunni-Shia tension even if it weren’t for Iraqi government policy. But former Prime Minister Nouri al-Maliki’s treatment of the Sunni minority helped ISIS considerably.
Maliki, a Shia Muslim who was prime minister from 2006 to 2014, built a Shia-dominated sectarian state and refused to take steps to accommodate Sunnis, who already felt disenfranchised by their loss of influence in 2003. Police killed peaceful Sunni protestors and used anti-terrorism laws to mass-arrest Sunni civilians. Maliki made political alliances with violent Shia militias, infuriating Sunnis. ISIS cannily exploited that brutality to recruit new fighters.
When ISIS reestablished itself, it put Sunni sectarianism at the heart of its identity and propaganda. The government persecution, according to the Washington Institute for Near East Policy’s Michael Knights, “played right into their hands.” Maliki “made all the ISIS propaganda real, accurate.” That made it much, much easier for ISIS to replenish its fighting stock.
That wasn’t the only way the Iraqi government helped ISIS grow, according to Knights. The US and Iraqi governments released a huge number of al-Qaeda prisoners from jail, which Knights called “an unprecedented infusion of skilled, networked terrorist manpower — an infusion at a scale the world has never seen.”
The prime minister who replaced Maliki, Haider al-Abadi, learned from his predecessor’s mistakes and made an effort to improve the situation. Among other things, he fired Maliki’s crony political appointees in the military and made a real effort to engage with the Sunni community.
But Abadi is seriously limited by the structure of Iraqi politics. He himself comes from a Shia Islamist political party, Dawa, part of the bigger State of Law political coalition. Many of the steps needed to address Sunni grievances — such as reforming laws limiting participation of former Saddam-era Ba’ath party members, who are largely Sunni, in government — were hard sells among Shia parties.