Without close air support and significant artillery and armor 2,500-5,000 Jihadi’s will probably “pwn” 20,000-25,000
Iraqi regulars trying to retake a metropolitan area of 1,000,000 people. 20,000 to 25,000 troops is “change under the car seat” in a city of a million + people.
The only mitigating factor I could see is if there is a boatload of residents that end up willing to pitch in to kick out ISIS after having had to live under them for a while.
Human shields galore.