From the bloody repression of peaceful protests against President Bashar al-Assad's regime to foreign intervention, below are key dates in Syria's civil war as it enters its eighth year.
The complex conflict has left more than 350,000 people dead, according to the Syrian Britain-based Observatory for Human Rights, while millions have been displaced and the country lies in ruins.
- Revolt and repression -
On March 15, 2011, unprecedented protests demand civil liberties and the release of political prisoners after 40 years of repressive rule by the Assad family.
Denouncing "an armed rebellion by Salafist groups", the regime represses demonstrations in Damascus and the southern city of Daraa but protests continue.
In July, defecting army colonel Riad al-Assad sets up the Turkey-based rebel Free Syrian Army (FSA). Islamist groups join the revolt.
- Air strikes, Hezbollah, Iran -
In March 2012, regime forces take control of the rebel stronghold in third city Homs after a month of bombardment. Other bloody operations are carried out, notably in the central city of Hama, after massive anti-regime protests.
In July, FSA fighters launch a battle for Damascus but the government holds firm.
From 2013, regime helicopters and planes unleash crude barrel bombs on rebel zones.
The same year, Iran-backed Lebanese Shiite militant group Hezbollah says it is fighting alongside Syrian government forces.
Iran also boosts its military support for longtime ally Assad.
- Chemical weapons -
In August 2013, Washington accuses the regime of killing more than 1,400 people with chemical weapons in rebel-held districts near Damascus.
In September, the United States and Assad ally Russia agree a plan to eliminate Syria's chemical weapons, averting punitive US strikes against the regime.
But forces on the ground, in particular from the regime, have since been accused again of using chemical weapons.
In April 2017, a sarin gas attack on the opposition-held village of Khan Sheikhun leaves more than 80 dead, prompting Washington to attack a regime air base.
- Rise of the jihadists -
In January 2014, hostilities between jihadists of the Islamic State of Iraq and the Levant (ISIL) and rebel groups turn into an open war in the north.
ISIL, the future Islamic State (IS) group, takes Raqa -- the first provincial capital to fall out of regime control -- from rebel forces.
The jihadist offensive allows Damascus to justify its fight as a battle against "terrorism".
- Coalition air strikes -
In September 2014, a US-led coalition launches air strikes against IS in Syria.
The strikes benefit Kurdish groups, which since 2013 have run autonomous administrations in Kurdish-majority areas and go on to oust IS from key areas.
- Russia to Assad's aid -
In September 2015, Russia launches air strikes in support of Assad's troops, who are on the back foot.
Russian firepower helps turn the tables for the regime, which begins to retake rebel-held territory, including the northern city of Aleppo in late December 2016.
In January 2017, Russia and Iran, as backers of the Syrian regime, and Turkey, supporting the rebels, organise talks in Astana, Kazakhstan, between representatives of both sides.
The process leads to the creation of four so-called "de-escalation zones", although sporadic fighting and bombardments continue.
- Turkish offensive -
In an added complication to the drawn-out conflict, Turkey launches an operation in January 2018 against the powerful Kurdish People's Protection Units (YPG) which played a key role in beating back IS.
The militia controls the Afrin region on the border with Turkey, and Ankara is wary of Kurdish aspirations for autonomy, labelling the YPG a "terror group".
- Blitz of Eastern Ghouta -
On February 18, the Syrian regime launches a ferocious assault on the remaining rebel-held enclave near Damascus, Eastern Ghouta.
In just over three weeks, the Russian-backed onslaught kills more than 1,100 civilians, according to the Observatory.