See this map: http://ichef.bbci.co.uk/news/624/cpsprodpb/83ED/production/_86737733_iraq_syria_air_strikes_624_v49.png http://ichef.bbci.co.uk/news/624/cpsprodp

See this map: http://ichef.bbci.co.uk/news/624/cpsprodpb/83ED/production/_86737733_iraq_syria_air_strikes_624_v49.png http://ichef.bbci.co.uk/news/624/cpsprodpb/83ED/production/_... Even if the whole IS is not always just fighting Assad, they are deep in the Assad controlled regions too (Assad is in Damascus look how near they are). A lot of "empty" area are the deserts.