The information for this testimony was gathered from a range of sources, including jihadist websites and forums, Western websites that publish jihadist videos and transcripts (such as SITE Intelligence Group and the Long War Journal), interviews with government officials from the West and the Middle East, and secondary sources. Yet there are notable gaps in this analysis, as there are in most assessments of the Syrian war. It is uncertain, for instance, how many foreign fighters from the West and other areas have traveled to Syria, why and how they have radicalized, and what they will do if they leave. Despite these methodological challenges, there is still sufficient information to assess the threat from Syria with reasonable accuracy. This testimony is divided into three sections. The first outlines the origins of Jabhat al-Nusrah and its evolution since 2011. The second section assesses Jabhat al-Nusrah’s growing capabilities and presence in Syria, as well as briefly describes other militant groups operating in Syria. The third examines the threat to the U.S. homeland and U.S. allies from Syria.