A massive explosion hit a key arsenal belonging to Iraq's Popular Mobilization Units (PMU) north of Baghdad on Aug. 19, the fourth and latest in a series of such attacks targeting the militia group's facilities in recent weeks.
The PMU came together in 2014 to tackle the rising threat of the Islamic State, which was making rapid advances to control large swaths of territory across Iraq. The Shiite-majority forces have since been backed and equipped by the government in neighboring Iran. The group is widely credited for its key role in the eventual defeat of the Islamic State and for helping flush the militant organization out of Iraq.