CRS – The Islamic State — Frequently Asked Questions: Threats, Global Implications, and U.S. Policy Responses,  John W. Rollins, Specialist in Terrorism and National Security. Heidi M. Peters, Information Research Specialist. November 19, 2015.

“When addressing threats emanating from the Islamic State (IS), numerous strategy and operational considerations arise that might be of interest to U.S. policymakers, especially in the wake of the deadly November 13, 2015, terrorist attacks in Paris IS activities and U.S. and coalition party policy and operational responses are an amalgam of complex , and at times competing , challenges. Since the establishment of IS, its strategic objectives and tactical activities have evolved, gaining strength in some areas and having its capability degraded in others. U.S. and other nations’ responses continue to evolve as the threat posed by IS changes.”