Despite the large number of foreign fighters, members of Iraq’s former Baathist army make up the majority of ISIS's military and security committees and its emirs and princes, according to the report.
The expertise the men bring help ISIS to outmaneuver the Iraqi and American militaries and the networks they developed for overcoming sanctions through smuggling are now helping ISIS with its oil trade, The Washington Post reports.
Even in Syria, the local emirs are shadowed by an Iraqi deputy who makes the decisions, a man using the pseudonym Abu Hamza told the Post. Abu Hamza became disillusioned with ISIS and eventually escaped to Turkey.
"All the decision makers are Iraqi, and most of them are former Iraqi officers. The Iraqi officers are in command, and they make the tactics and the battle plans," Abu Hamza told the Post. "But the Iraqis themselves don’t fight. They put the foreign fighters on the front lines."
Experts told the Post that the former Baathist members were steered to ISIS when the Iraqi army was disbanded after the American invasion of 2003. The Iraqi forces were barred from government employment and pensions, but were allowed to keep their weapons.
Facing poverty for years, many responded to ISIS leader Abu Bakr al-Baghdadi's recruitment.Hassan Hassan, a Dubai-based analyst and co-author of the book “ISIS: Inside the Army of Terror.”
The American military didn't recognize early on the role of the former Baathist officers, instead blaming foreign fighters, Col. Joel Rayburn of the National Defense University said.
"We might have been able to come up with ways to head off the fusion, the completion of the Iraqization process," he said.
Though the strict Islamic dogma of ISIS appears at odds with the secular rule of Saddam, the Iraqi government had actually been moving toward a form of religious rule since just after the first Iraq War in the early 1990s, according to the Post.
Iraq under Saddam had begun cutting off the hands of thieves and beheading women accused of prostitution. Saddam's forces also ruled by intimidation, as does ISIS.
"Former Baathist officers recall friends who suddenly stopped drinking, started praying, and embraced the deeply conservative form of Islam known as Salafism in the years preceding the U.S. invasion," the Post reported.
Some of those officers had joined the U.S.-backed Awakening movement and fought al-Qaida in Iraq, which preceded ISIS. But after American troops were withdrawn, along with support for Awakening fighters, many joined ISIS.
ISIS leadership fears being infiltrated by spies, and, therefore, keeps fighters at a distance, working through intermediaries and keeping their identities secret, Abu Hamza told the Post.
He called the foreign fighters he was involved with "good Muslims," but he didn't have the same opinion of Iraqi leaders.