Resistance groups during WWII were not warring with each other by religious sect, tribes, family grudges, local warlords, etc. At least I have never read or heard that they were.
The problem we don’t know who is the ‘resistance’ in these place ... or what they are resisting.
The alternative is siege or frontal assault on a fortified position, very messy. If the locals can thin the ranks and keep ISIS worried about their 6, taking the city would be easier. Assuming that's what we want...