Syria, where a US-led coalition launched its first strikes on Islamic State jihadists Tuesday, has been wracked for the past three and a half years by a devastating civil war.

The conflict erupted in March 2011 with the repression of peaceful pro-reform protests, prompting an armed uprising against the regime of President Bashar al-Assad.

It has become many-sided as jihadists gain ground, notably the Islamic State group and the Al-Qaeda affiliated Al-Nusra Front.

A timeline:

-- 2011 --

- March 15-16: First protests demanding greater civil liberties and freedom for political prisoners. The regime cracks down heavily in Damascus and Daraa, the cradle of the uprising, denouncing "an armed rebellion by Salafist groups".

- March 23: Crackdown reportedly kills 100 people in Daraa.

- July 30: Creation of the Free Syrian Army (FSA), made up of civilians who have joined the rebellion, backed by army deserters.

- August 18: US President Barack Obama and his allies urge Assad to quit. Western and Arab states later impose sanctions on his regime.

- October 4: Russia and China veto for the first time a draft UN resolution condemning Damascus for the crackdown.

-- 2012 --

- July 18: Damascus bombing kills four top security officials, including Assad's brother-in-law Assef Shawkat.

- July 20: Rebels launch a major assault on second city Aleppo. On July 28 the military launches a counter-offensive.

- November 11: The opposition signs a unity deal in Doha to form the National Coalition.

- December 10: Al-Nusra Front seizes a strategic army base in Aleppo, to the FSA's detriment.

-- 2013 --

- June 5: The army recaptures the key town of Qusayr after an assault led by fighters from Lebanon's Hezbollah.

- August 21: Troops launch an offensive in the Damascus suburbs. The opposition accuses the army of chemical weapons strikes around the capital, where hundreds are killed. The government denies responsibility and blames rebels.

- September 14: Washington and Moscow agree on a plan to eliminate Syria's chemical weapons by the middle of 2014, putting off the threat of punitive strikes against the Assad regime by Washington and Paris.

-- 2014 --

- January 22: In Geneva, the warring parties sit down for the first time to seek a political settlement. On February 15, a second round of talks ends without result.

- May 9: Syrian troops enter the Old City of Homs, after a two-year total army blockade and near-daily bombardment. Rebels withdraw.

- June 3: Assad wins a new seven-year term in a poll, held only in government-held areas, branded "illegitimate" by the opposition and a "non-election" by Washington.

- June 29: Jihadists from the Islamic State of Iraq and the Levant (ISIL), declare a "caliphate" across swathes of territory in Iraq and Syria. They rename themselves the Islamic State (IS), and the move is rejected by a great majority of Islamic groups.

- September 23: The US and Arab allies launch strikes against IS militants in the first foreign intervention in Syria since the start of the conflict.