Don’t overlook how difficult it is to combat IED attacks. Most are emplaced at night and in many areas we had IR reconnaissance balloons, Specter gunships, Kiowas, Apaches, drones and other IR assets aloft looking for them at night.
Considering the IA’s assets and abilities I think their best tactic is to swarm an area and kill all the fighters and anyone who flees. It’ll be expensive in martyr power but it will work. This is how the Russians defeated the Germans in ‘43 - ‘45.
The Russians were staunch because it was clear that their choice was between (1) beat the Germans back or (2) be exterminated for not being of Aryan blood as Hitler defined it. Shiites can always convert to the majority Sunni sect. Islam triumphed very rapidly during its first centuries in part because the losers knew they could always convert. (Arabia's neighbors had also been decimated by the plague). They were held back only by fear of divine punishment via weather calamities, plagues, et al. Once it became clear their traditional gods were indifferent to their conversion to Islam (or perhaps wholly notional), mass conversions occurred just to avoid having to pay jizya.
Without overwhelming Western material superiority, they will need to fight by the same medieval rules as their ISIS adversaries. There are sound military reasons for fighting that way, which is why medieval armies used to do it. Genghis Khan's small army would have been nickel-and-dimed to death if he hadn't whacked entire cities for daring to revolt against the tiny garrisons he deployed in the conquered lands to his rear.