The Islamic State of Iraq and the Levant, or ISIL, poses a domestic terrorism threat to the America. While ISIL seems to have reared its head only in the last 18 months, a closer look quickly reveals ISIL to be an old foe; one with whom the United States has done battle for more than a decade. Before the group declared itself a global caliphate and adopted its current name, it was merely the Islamic State of Iraq. During war, members of this same group were among the most prolific perpetrators of attacks against American troops and our partners in Iraq. The procession of name changes, however, has made no difference to ISIL's commitment to harm Americans. We were reminded of this with the death of Kayla Mueller after 18 months of ISIL captivity; the 26-year-old, from Prescott, Arizona, had traveled to Syria with Doctors Without Borders to help alleviate the suffering brought there by Islamic extremism.