Timeline: Syria's years of blood

BEIRUT (Reuters) - 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 2011 - The first protests against President Bashar al-Assad quickly spread across the country, and are met by security forces with a wave of arrests and shootings.

- 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.

- 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 has declared 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.

- January 2014 - An al-Qaeda splinter group seizes Raqqa before grabbing swathes of territory across Syria and Iraq, declaring a new caliphate and renaming itself Islamic State.

- 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.

- September 2014 - Washington builds an anti-Islamic State coalition and starts 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, but Islamist militants are taking 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.

- 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 - The Syrian army and its allies defeat rebels in their biggest urban base of Aleppo after months of siege and bombardment, confirming Assad’s growing momentum.

- January 2017 - Russia, Iran and Turkey meet in Astana, Kazakhstan, in parallel with the faltering U.N. peace effort, to create “de-escalation zones” that fail to stop the fighting.

- March 2017 - Israel acknowledges having conducted air strikes against Hezbollah in Syria, aiming to degrade the growing strength of Iran and its allies.

- April 2017 - The United States launches a cruise missile attack on a Syrian government airbase near Homs after a poison gas attack on the rebel-held town of Khan Sheikhoun.

- November 2017 - U.S.-backed, Kurdish-led forces defeat Islamic State in Raqqa. That offensive, and a rival one by the Syrian army, drives the jihadist group from nearly all its land.

- April 2018 - The Syrian army recaptures eastern Ghouta, before quickly retaking the other insurgent enclaves in central Syria, and then the rebels’ southern bastion of Deraa in June.

- August 2018 - Pro-government forces mobilise for a major assault against Idlib and adjacent areas.