ISIS militants have taken control of towns in Iraq and Syria . The group includes jihadists who have traveled from Europe and elsewhere to fight . Al Qaeda in Pakistan taught many European and American recruits how to make high-explosive bombs out of readily available materials . Citizens from Iraq , Denmark , Germany , U.S. have carried out bombings in Denmark and Syria . Security experts are concerned that jihadists militants may return home to cause chaos .
ISIS militants have taken control of towns in Iraq and Syria . The group includes jihadists who have traveled from Europe and elsewhere to fight . Citizens from Iraq , Denmark , Germany , U.S. have carried out bombings in Denmark and Syria . Security experts are concerned that jihadists militants may return home to cause chaos .