I'll spell it out slowly so even the DUmmies understand.....end-fill-trey-shun ......or for the more literate, infiltration.
They can infiltrate the city with suicide bombers with ease and destroy any resistance. May be costly to ISIS in lives but what do they care as long as Allah has plenty of virgins on hand.
Muslims killing Muslims is good....the next best thing is DUmmies killing DUmmies and that day will come when they get their great socialist utopia.