The unending Syrian conflict has become the most prolonged and bloodiest since the start of the twenty-first century. It carried off the lives of millions of Syrian, turned the country into a battlefront and caused an immigration crisis in Western states. Moreover, a new fear threatened the world—an emergence of international terrorism, which not only damaged regional security, but also plunged many European capitals into a chaos.   Such a situation could not be ignored by major players on the international scene, including the United States which has been involved in the Syrian crisis since...