Unlike many Islamic State commanders, Qaduli came from Osama bin Laden’s al Qaeda rather than the dissolved Baath party of Saddam Hussein, who was toppled by a U.S.-led invasion in 2003.

He was arrested several times under Saddam because of his extremist religions opinions and went to Afghanistan in 1998, where he met bin Laden, Hashimi said.

Bin Laden wanted him to take over command of the group’s Iraq franchise in 2010. But Baghdadi, already settled in as the local commander, turned against al Qaeda in 2013 and declared himself caliph a year later, winning the backing of Qaduli, Hashimi said.

Apparently from Hussein's Baath Party which dissolved when the US attack Iraq.

Islamic State Dealt Hefty Body Blow With Death Of Top Aide: Officials