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 Islamic State. This is the story of the civil war so far, in eight short chapters.
1. 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.
2. 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. However, by August 2014 that figure had more than doubled to 191,000 - and continued to climb to 250,000 by August 2015, according to activists and the UN. The conflict is now more than just a battle between those for or against President Assad.
3. War crimes
A UN commission of inquiry, investigating alleged human rights violations since March 2011, has evidence that those on both sides of the conflict have committed war crimes - including murder, torture, rape and enforced disappearances. Government and rebel forces have also been accused by investigators of using civilian suffering - such as blocking access to food, water and health services - as a method of war.
In February 2014, a UN Security Council resolution demanded all parties end the "indiscriminate employment of weapons in populated areas". Since then, activists say, more than 6,000 civilians have been killed by barrel bombs dropped by government aircraft on rebel-held areas. The UN says in some instances, civilian gatherings have been deliberately targeted, constituting massacres.
Islamic State has also been accused by the UN of waging a campaign of terror in northern and eastern Syria. It has inflicted severe punishments on those who transgress or refuse to accept its rule, 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.