Some estimate that IS and its allies control about 40,000 sq km (15,000 sq miles) of Iraq and Syria - roughly the size of Belgium. Others believe they control closer to 90,000 sq km (35,000 sq miles) - about the size of Jordan. That territory includes cities - Mosul, Tikrit, Falluja and Tal Afar in Iraq; Raqqa in Syria - oil fields, dams, main roads and border crossings.