The territory controlled by the ISIS is vast and spreads across wide areas of Iraq and Syria. To date ISIS has proved resilient in the face of American airstrikes, Kurdish Peshmerga fighters, Iranian-backed Shia militias, battle-hardened Syrian rebels, Asad regime forces, and even other jihadist groups.
ISIS burns through cash, spending on military hardware, equipment, infrastructure, safe houses, mass transportation, food, and its own high-quality media center, al-Hayat (the life) and a magazine called Dabiq, not to mention tens of thousands of fighters operating in the field. No matter how much the group spends, it makes an estimated $6 million from these sources every day. There may be no limit to how much the group can expend in its effort to further its ideology.