More than 250,000 Syrians have lost their lives in four-and-a-half years of armed conflict, which began with anti-government protests before escalating into a full-scale civil war. More than 11 million others have been forced from their homes as forces loyal to President Bashar al-Assad and those opposed to his rule battle each other - as well as jihadist militants from so-called Islamic State. This is the story of the civil war so far, in eight short chapters.
- Uprising turns violent
Pro-democracy protests erupted in March 2011 in the southern city of Deraa after the arrest and torture of some teenagers who painted revolutionary slogans on a school wall. After security forces opened fire on demonstrators, killing several, more took to the streets.
The unrest triggered nationwide protests demanding President Assad's resignation. The government's use of force to crush the dissent merely hardened the protesters' resolve. By July 2011, hundreds of thousands were taking to the streets across the country.
Opposition supporters eventually began to take up arms, first to defend themselves and later to expel security forces from their local areas. - Descent into civil war
Violence escalated and the country descended into civil war as rebel brigades were formed to battle government forces for control of cities, towns and the countryside. Fighting reached the capital Damascus and second city of Aleppo in 2012.
By June 2013, the UN said 90,000 people had been killed in the conflict. By August 2015, that figure had climbed to 250,000, according to activists and the UN.
The conflict is now more than just a battle between those for or against Mr Assad. It has acquired sectarian overtones, pitching the country's Sunni majority against the president's Shia Alawite sect, and drawn in regional and world powers. The rise of the jihadist group Islamic State (IS) has added a further dimension.
A UN commission of inquiry has evidence that all parties to the conflict have committed war crimes - including murder, torture, rape and enforced disappearances. They have also been accused of using civilian suffering - such as blocking access to food, water and health services through sieges - as a method of war.
The UN Security Council has demanded all parties end the indiscriminate use of weapons in populated areas, but civilians continue to die in their thousands. Many have been killed by barrel bombs dropped by government aircraft on gatherings in rebel-held areas - attacks which the UN says may constitute massacres.
IS has also been accused by the UN of waging a campaign of terror. It has inflicted severe punishments on those who transgress or refuse to accept its rules, including hundreds of public executions and amputations. Its fighters have also carried out mass killings of rival armed groups, members of the security forces and religious minorities, and beheaded hostages, including several Westerners.
http://www.bbc.com/news/world-middle-east-26116868
- Humanitarian crisis
More than 4.5 million people have fled Syria since the start of the conflict, most of them women and children. Neighbouring Lebanon, Jordan and Turkey have struggled to cope with one of the largest refugee exoduses in recent history. About 10% of Syrian refugees have sought safety in Europe, sowing political divisions as countries argue over sharing the burden.
A further 6.5 million people are internally displaced inside Syria, 1.2 million were driven from their homes in 2015 alone.
The UN says it will need $3.2bn to help the 13.5 million people, including 6 million children, who will require some form of humanitarian assistance inside Syria in 2016. About 70% of the population is without access to adequate drinking water, one in three people are unable to meet their basic food needs, and more than 2 million children are out of school, and four out of five people live in poverty.
The warring parties have compounded the problems by refusing humanitarian agencies access to civilians in need. Up to 4.5 million people in Syria live in hard-to-reach areas, including nearly 400,000 people in 15 besieged locations who do not have access to life-saving aid.