Your frame of reference is... interesting. "Dispels any doubts". As if we didn't know? That is a lie to help sell a narrative, to help propagandize.
- ISIS is Sunni.
- Iran is Shi'ite.
After the fall of Mosul, the remaining half of Iraq was Shi'ite, and friendly to Iran. Iranian military advisors entered Iraq and assisted in the creation of the Shi'ite Militias that played the ground war and defeated ISIS.
These Iranian commanders became Iraqi war Heroes.
2016: Even more troubling to the U.S. military are reports that Qassem Soleimani, an Iranian general who commands the Islamic Revolutionary Guard’s Quds Force, is now on the ground outside Mosul ahead of an expected operation to retake Iraq’s second-largest city which has been under ISIS control for the past two years.