Syrian war began as a peaceful uprising against Syria’s president Basher al-Assad from 2011.
He was alleged for unemployment, corruption and lack of political freedom under his rule in the country.
In March 2011, Syrians were inspired by the Arab spring and they erupted in the southern city of Deraa.
Mr. Assad used deadly force to crush the aggressor. As a result, Syrian people started demanding the president’s resignation.
Then opposition supporters began to take up arms to defend themselves and to expel security forces from their local areas.
The violence rapidly grew and the country turned into civil war.
Hundreds of rebel brigades were formed to battle against government forces for control of the country.
The rise of jihadist groups has added a further dimension to the war.
Meanwhile Islamic state which controls large swathes of northern and eastern Syria has been fighting against government forces.
From early stages of the Syrian conflict, Russia delivered ammunition and weapons to the Syrian government
Thousands of Shia militia men from Iran, Lebanon, Iraq, Afghanistan and Yemen are fighting alongside the Syrian army to protect holy sites.
As Syria is the main transit point for Iranian weapons shipments they have sent thousands of fighters to support government forces.
U.S has been carrying out air strikes on Syria since 2014.
In the first intentional attack on Syria itself, U.S hit an air base which it said was behind a deadly chemical attack, in April 2017.
Now rebel fighters and allied jihadists are estimated to control about 15% of Syrian territory.
The conflict had caused 470,000 deaths and around five million people have fled Syria.