What started as a local protest movement in Syria's southern city of Dara'a expanded into a full-fledged civil war by 2012. ISIS, which grew out of al-Qaeda in Iraq, took root in northern and eastern Syria in 2013 after seizing swaths of territory in neighboring Iraq. The jihadist group is fighting to overthrow Syrian President Bashar al-Assad's regime and establish a caliphate.
The Syrian Civil War has pulled in the United States, Russia, Iran and almost all of Syria's neighbors. It has become the largest humanitarian crisis since World War II, according to the United Nations.