Presently Syrian Conflict is not a civil war in which only peoples of the country fight. This is a proxy war now. To understand the Syrian Conflict, you need to know who is fighting and for what they are fighting.
First of all, there are 5 major groups who has been fighting in Syrian Conflict with their own visions.
- The present Government, i.e. Bashar Al-Assad for his own Assad Regime.
- Moderate Rebel Group, originated from Sunni Syrian citizens.
- Kurd Group, originated from Kurdish community of Syria.
- ISIS, supporters of Islamic Caliphate.
- Al-Nusra Front, a branch of Al-Qaeda in Syria.
Countries who are participating in Syria crisis :
- Assad Regime => Russia, Iran ( Shia Country ) and China ( Diplomatically ).
- Moderate Rebel i.e. Free Syrian Army (FSA) => USA, Gulf States [Saudi Arabia, Qatar], Turkey, Jordan.
- Kurd Group => USA.
- ISIS => Leader is Abu Bakr al-Baghdadi.
- Jabhat Al-Nusra => A branch of Al-Qaeda.
Actually the reason behind the fight became religious is, the president of Syria Bashar Bashar Al-Assad belongs to Shia Muslim. But Shia Muslim in Syria is not more than 13 % of total population whereas more than 83 % peoples belongs to Sunni Muslim. As a result majority Sunni did not want to be controlled by Shia president.Hafez Al-Assad was previous president of Syria [1973 – 2000]. Hafez Al- Assad died on 10th June 2000. Then his son Bashar Al- Assad became the president.Firstly, the collision of Syria was between Assad Regime (Government) and Civil Population of the country. Collision started due to poverty, unhealthy life, poor education system during 2007-2010. Another major reason was political suppression on all minorities. But as the time passed, the fight became a religious fight.
Beginning of Syrian civil war : 
The struggle began on 2010 in the form of street protest against Assad Government. Sunni civilians want a democratic secular government. But Bashar Al-Assad do not want to lose president ship. Therefore struggle became a large civil war.
Large scale Syrian civil war by Syrians : 
Arab Spring successfully over threw the Dictatorship government of Tunisia in January 2011. Inspired peoples of Syria also started their protest with full force. But on March 2011, Assad launched an attacked on civil protesters to stop their influence in the country. As a result the protester became more determined. Peoples of government army left their job. On July, they formed Free Syrian Army (FSA). That group was a moderate rebel group of Sunni Muslim. In the meantime Al-Assad released jihadist from jail to join FSA. He did that to name FSA as a jihadist group so that no country try to help FSA.
On other hand, World Extremists Sunni Muslim started gathering in Syria to fight against Shia Muslim. An extremist group Jabhat Al Nusra was formed. This was a branch of Al Qaeda. Free Syrian Army (FSA) and Jabhat Al-Nusra started fighting together against Assad Government.
In some parts, another minority group called Kurd was also fighting for freedom from Assad Regime. Kurd were also victim of regular discrimination and harassment by the government. They formed their rebel group called Syrian Democratic Forces (SDF). SDF started capturing and controlling their area. Yet, the fight was between three sides.
|1. The Government|
2. Sunni Population (FSA) and
3. Kurd Community
Foreign Interference in Syrian Conflict : 
Iran started helping the Government. This is the largest Shia country of the world. So Iran want Shia to control Syria. On the contrary, Turkey and Gulf States (Like Saudi Arabia, Qatar) started helping the Rebel Groups. Because Gulf States support Sunni Muslim. So they want to establish Sunni government there. As a result Iran became helper of government and Gulf states became helper of Rebel Groups.
Iran took a different step. They started helping a group called Hezbollah to counter Rebels directly.
U.S interference in Syrian Conflict : 
Gulf States started sending more money and weapons to the Rebel groups. Jordan also joined Saudi Arabia and they also started helping Rebels. So at the mid of 2013, two sides were fighting to each other. Assad and Iran in one side, who are Shia Muslim supporters. On the other side Gulf States, Jordan and Rebels. They are Sunni Muslim supporters.
Finally USA came to start a peace process. The USA government ordered CIA to train Free Syrian Army (FSA) and other Moderate Rebel Groups. Because USA wanted to establish a secular democratic government. So USA requested Saudi Arabia not to support Extremist of Rebels Groups. The reason is, extremist group Jabhat Al-Nusra had a plan to strike USA after achieving Syria.
Assad was becoming weaker and weaker. On August 2013, Assad government again launched an attacked on Rebels as well as civilians by Chemical weapons. The attack made the world shocked. Attack was made in Ghouta area. More than 700 peoples died.
Then USA made and agreement with the Rebels Group and Gulf States and started helping Rebels directly. After the agreement, extremist groups separated from Moderate Rebel Groups. They started fighting Assad separately. At that moment Assad found two enemy groups. One is Moderate Rebels group and another is Extremist groups.
USA and Moderate Rebels groups wanted to set up secular democracy but Extremist wanted to set up Caliphate in Syria. The different ideology it made it very difficult to remove Assad from government.
Formation of ISIS in Syria : 
All Extremist Groups was joining ISIS. On February 2014, ISIS started fighting under the leadership of Abu Bakr al-Baghdadi. ISIS was attacking both the Moderate Rebels Groups and Assad Government .
As ISIS started attacking Rebels group supported by USA, ISIS became the main enemy of USA. Another reason was, USA did not wanted Caliphate to be establish in Syria. USA planed to bomb only ISIS. Kurds were helping Moderate Rebels group by attacking ISIS. But for some reasons Turkey started bombing Kurds. Ultimately ISIS got an indirect help from Turkey. Finally after a certain period ISIS captured a large area of Syria and established Caliphate.
During that period the Syrian map was like this…
1.Yellow => KURDS
2.Grey => ISIS
3.Green=> Free Syrian Army
4.White => Jabhat Al Nusra
5.Red => Bashar Al Assad i.e. The Syrian Government.
Hence, Assad was in trouble. Four major groups captured a large area of Syria. Government had no control over those areas. Then Russia came forward to help Assad. Russia wanted to provide Assad full control over Syria. Russia started bombing ISIS, Rebels Groups, Kurdish Groups thoroughly. As a result Assad Government captured some of its lost areas in two years. Again all Anti-Assad groups started losing their lands and control.
Back step of U.S from Syria crisis : 
After Donald Trump came in power in USA, the government decided to keep USA out from Syrian matters. USA thought it would be better for peace if Assad stay in power. But Assad’s one step forced USA to rethink. Assad again attacked Rebels groups with chemical weapons. In response USA started bombing air bases of Syrian government. That was the first time USA directly attacked Assad Government.
Actually, Bashar al-Assad belongs to Ba’ath party, the same party Saddam Hussein of Iraq belonged to. This may be the reason USA do not like Assad.
Presently all five groups are fighting with each other for their own vision. USA, RUSSIA, ARAB, TURKEY and many other countries are directly or indirectly involved in Syrian Crisis.
Steps taken by UNESC to stop Syrian Conflict :
On 2012, Geneva-1 resulted cease fire only for few days. But War started again.
2014, Geneva- II resulted the same.
2015, Vienna Process kept peace for more than 3 months.
2016, Geneva-III also could stop war for a short period. Ultimately the result was same.
Spoiled human Life due to Syria crisis :
The Syrian Conflict is not going to solve yet. According to Syrian Centre for Policy Research, approximately 55,000 Syrian Children died and in total more than 470,000 people died in last five years . Average life expectancy dropped from 75 Years to 50 Years. United Nations High Commission for Refugee said Syrian crisis is the worst situation on earth after WW-II. Some experts also called Syrian Conflict WW-III.