Numerous armed groups, including terrorists such as Islamic State (ISIL, also known as Daesh), as well as opposition factions, have been fighting in the Syrian civil war against forces loyal to Syrian President Bashar Assad.
The internal conflict in Syria has lasted for about five years, claiming hundreds of thousands of lives. A September ceasefire, negotiated by the United States and Russia, has failed to hold.
Russia has been supporting Syria's legitimate authorities, the government of President Bashar Assad, in the Syrian civil war, which started in 2011. Washington has sided with the so-called "moderate opposition" that has been fighting against Syrian government forces along with other groups.