"The rise of the insurgent terrorist group known as the Islamic State (IS, also known as ISIL, ISIS, or the Arabic acronym Da'esh) and Russia's military intervention on behalf of the Syrian government have reshaped debates over U.S. policy toward the ongoing civil conflict in Syria, now in its sixth year. The Islamic State controls large areas of northeastern and central Syria, from which it continues to launch assaults on forces opposed to and aligned with the government of President Bashar al Asad. Meanwhile, fighting elsewhere pits government forces and their foreign allies against a range of anti-government insurgents, some of whom receive limited U.S. assistance. Russian military intervention in support of Asad poses a direct challenge to U.S. goals in Syria, and has raised new questions about the future of the conflict and U.S. strategy. Since March 2011, the conflict has driven more than 4.8 million Syrians into neighboring countries as refugees (out of a total population of more than 22 million). More than 6.3 million other Syrians are internally displaced and are among more than 13.5 million Syrians in need of humanitarian assistance. The United States remains the largest bilateral provider of such assistance, with almost $6 billion in U.S. funding identified to date. [...] U.S. officials and Members of Congress continue to debate how best to pursue U.S. regional security and counterterrorism goals in Syria without inadvertently strengthening Asad, the Islamic State, or other anti-U.S. armed Islamist groups. [...]"
CRS Report for Congress, RL33487
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html