The United States and its allies have carried out at least 5,000 airstrikes against the so-called Islamic State since August 2014. While the campaign has proved effective in halting the terror group's
territorial gains, it has not stopped the flow of foreign fighters into the region. In 2012, there were an estimated 3,500 foreign militants in Syria
and Iraq, a number that grew to over 25,000 in 2015. Tunisia is the largest origin country, followed by Saudi Arabia and Jordan.