About 560,000 people have been killed since the Syrian war began March 2011, the Syrian Observatory for Human Rights said in an updated death toll released Monday.
The update comes as Syria braces for a new battlefront in the northwest. This timeline shows how the war flared, the country splintered, foreign powers were drawn in, peace-making efforts failed, and Russia eventually helped Damascus drive back rebels.
March 6, 2011 - Fifteen teenagers are arrested for writing "the people want the regime to fall" on walls across the city of Deraa.
March 15, 2011 - Hundreds of people stage "Day of Rage" protests in Damascus and Aleppo, calling for democratic reforms. Protest in Damascus is violently dispersed.
March 16, 2011 - Protest is held at Marjeh Square in Damascus, near the Interior Ministry, calling for release of political prisoners. Police arrest several of the protesters.
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In Deraa a protest is held in response to arrested teenagers.
March 17- Demonstrations continue across Syria demanding release of the teenagers detained since 6 March and calling for democracy, greater political freedom and an end to corruption. In Deraa police open fire killing four people.
March 20, 2011 - Protesters burn Deraa's Ba'ath Party headquarters, the town's main courthouse and a branch of the Syria Telephone company owned by Rami Makhlouf, Assad's cousin
March 21, 2011 - To calm that situation, president Assad orders the release of the teenagers detained since March 6 and removes provincial governor Faisal Kulthum from his office. Troops are sent to Deraa
March 23, 2011 - In Deraa Syrian Army police confronted protesters gathered around the Omari mosque in the city centre, dispersing the crowd with tear gas and live ammunition.
March 29, 2011 - Syrian President Bashar al-Assad accepts his government's resignation. Tens of thousands of Syrians demonstrate in support of Assad.
April 16, 2011 - A new Syrian cabinet was sworn in. President Assad addresses the cabinet in a televised speech.
April 25-30 - Between April 25 and May 16, 2011, the Syrian army attacks and occupies Deraa. The army reportedly deployed 20 or 30 tanks, between hundreds and 6,000 troops, snipers on roofs, and helicopters with paratroopers for a battle at the Omari Mosque on April 30. At least 244 civilians and 81 soldiers were killed.
April 29, 2011 - Dubbed "Great Friday", anti-government protests are held in at least 20 towns across Syria. Security forces quelled the protests with live ammunition and tear gas.
May 5 - Siege of Homs. About 100 tanks and troop transports converge on the town of Al-Rastan, after anti-government protesters toppled a statue of the late Syrian president Hafez al-Assad and pledged to press ahead with their revolution despite sweeping arrests by Bashar al-Assad's government
May 7 - Military siege of Baniyas begins
May 8 - - Military siege of Tefas
May 11, 2011 - Tanks are sent into Homs and shelling begins
June 14, 2011 - For the first time, the Arab League condemns Syria's crackdown and repression
June 16, 2011 - UN Chief Ban Ki-moon condemns the violent crackdown on protesters
June 20, 2011 - In an hour-long noon address, President Assad blames "vandals", "radical and blasphemous individuals", and "foreign conspiracies" for the unrest, but also admits that some of the demands of protesters are legitimate.
June 21, 2011 -The Syrian government encourages all members of the Baath party to host pro-Assad rallies.
June 24, 2011 - For the first time, people in central Damascus begin protesting, and are immediately shot at outside the local mosque, killing 6. Approximately 15,000 people protest on the highway linking Damascus to Aleppo.
July 2011 - Some protesters take up guns and military units defect as the uprising becomes an armed revolt that will gain support from Western and Arab countries and Turkey.
July 11, 2011 - Supporters of President al-Assad attack the embassies of France and the United States in Damascus. No casualties were reported.
August 3, 2011 - Following increased violence in the preceding days, the United Nations Security Council for the first time condemned the human rights violations against the Syrian protesters.
August 4, 2011 - Assad issues a decree authorizing the formation of multiple political parties in Syria, as well as election reforms aimed at appeasing protesters
January 2012 - A bombing in Damascus is the first by al Qaeda's new Syrian affiliate, the Nusra Front, which gains in power and starts crushing groups with a nationalist ideology.
June 2012 - World powers meet in Geneva and agree on the need for a political transition, but their divisions on how to achieve it will foil years of U.N.-sponsored peace efforts.
July 2012 - Assad turns his air force on opposition strongholds, as rebels gain ground and the war escalates with massacres on both sides.
April 2013 - Lebanon's Hezbollah helps Assad to victory at Qusayr, a battle seen as halting rebel momentum and demonstrating the Iran-backed group's growing role in the conflict.
August 2013 - Washington declares chemical weapons use a red line, but a gas attack on rebel-held eastern Ghouta kills scores of civilians without triggering a U.S. military response.
May 2014 - Rebels in the Old City of Homs surrender, agreeing to move to an outer suburb - their first big defeat in a major urban area and a precursor to future "evacuation" deals.
June 2014 - Islamic State of Iraq and Syria militants declare "caliphate" in territory from Aleppo to eastern Iraqi province of Diyala.
September 2014 - Washington and five Arab countries build an anti-Islamic State coalition and start air strikes, helping Kurdish forces turn the jihadist tide but creating friction with its ally Turkey.
March 2015 - With better cooperation and more arms from abroad, rebel groups gain more ground and seize the northwestern city of Idlib. Islamist militants start playing a a bigger role.
September 2015 - Russia joins the war on Assad's side, deploying warplanes and giving military aid that soon turns the course of conflict decisively against the rebels.
December 2015 - Homs, Syria's third largest city returns to government control after four years of conflict. Syrian Army allows rebels to evacuate remaining area of Homs.
March 2016 - Syrian government forces with Russian air assistance drive Islamic State out of Palmyra, but are defeated again in December.
August 2016 - Alarmed by Kurdish advances against Islamic State along much of the border, Ankara launches an incursion with allied rebels, building a new zone of Turkish control.
December 2016 - Aleppo is recaptured by pro-government troops, backed by Russian jets and Iranian-sponsored militias.