Since the start of Syria's conflict, it has killed hundreds of thousands, driven millions from their homes and disturbed the "regional balance of power".
Syrian civil war has always been multi-sided with many confusing, transient multi-layered coalitions. Non-state actors, habitual "actors" of middle east including the US, Russia, Iran, Turkey, Syria, Israel, Saudi Arabia, Qatar, Lebanon, Egypt and so on. Let's address the elephant in the room: Syrian civil war has been more than Islamic State. Now, we can clearly see, even the Islamic State is at the edge of defeat, the war in Syria keeps deepening.
Assad government against rebels:
In 2011, a revolt began in Syria against the "dictatorship of Assad", its crackdown led to an armed struggle and finally a civil war. The rebels initially put Assad in distress but remained internally divided, and radical Islamists took their footsteps. Since Russia intervened on the government side in autumn 2015, Assad and its supporters - including Iran and Lebanon's Hezbollah militia - are on the road to victory. They all speak of the "fight against terrorism". Assad wants to recapture the whole country - one rebel bastion after another. Current attack targets are the Eastern Ghouta and the province of Idlib, two of the last rebel areas. For the civil population, that means: starvation, air strikes, expulsion. The war has claimed the lives of hundreds of thousands since 2011.
Turkey against Kurds:
In the course of the Syrian civil war, Kurds gained control of large parts of northern Syria through their fight against Islamic State (IS). This situation displeases Turkey, especially Erdogan, which sees the Kurdish YPG rebels as an offshoot of PKK, the group that has waged a three-decade insurgency against Turkey. Several times the Turkish army invaded northern Syria this year; currently, Turkey launched an air and ground offensive last month on the Afrin region to target Kurdish fighters in northern Syria. According to the Turkish government, no Kurds should rule west of the Euphrates.
US and Kurds against IS:
Islamic State had conquered large parts of Iraq and Syria in 2014. Since 2016, IS has lost almost all of its territories again - in Iraq to the government, in Syria to the Kurdish YPG and Syrian Democratic forces (SDF), who are supported by the US and the international coalition. This causes escalated tensions between the US and Turkey.
Russia vs the US:
The US-backed YPG ran in 2017 a race with Syria's government for the IS areas in eastern Syria. East of the Euphrates, the YPG prevailed, to the west of it Assad did. Now, in the east of Syria, the US and Russia are as close to each other as nowhere else in the world. And this is more than being geographically adjacent. The Russian government has admitted that dozens of Russians were killed or injured in a US air strike in Deir al-Zor on 7th of February.