The Battle for Aleppo

Following are key dates in the battle for Syria's second city Aleppo, where the army has gained significant ground in its offensive to recapture the entire city.

- Dragged into war -- April-May 2011: Thousands of students demonstrate in Aleppo, a northern city that had been spared the sort of violent protests that erupted elsewhere in the country. The protests are swiftly crushed by security forces and rival students who back the regime of President Bashar al-Assad.

- July 20, 2012: Fierce fighting breaks out between the army and rebels of the Free Syrian Army, a group of armed civilians and army deserters, in several city districts.

- In August the same year, troops backed by heavy artillery and warplanes secure central Christian neighbourhoods after a two-week offensive.

Since then, the city has been divided between loyalist districts in the west, where around 1.2 million people live, and rebel-controlled areas in the east that have a population of about 250,000. Each side has tried to wear the other down.

Aleppo province has become a theatre of operations for most of the factions fighting in Syria's war.

They include the Islamic State (IS) group, the Fateh al-Sham Front, which changed its name from Al-Nusra Front after renouncing its ties to Al-Qaeda, various rebel groups, the army and pro-regime militias, Lebanese Hezbollah fighters and Kurdish militiamen.

- Barrel bombs -- December 15, 2013: Regime air strikes using "barrel bombs" on rebel districts kill 76 people, according to the Syrian Observatory for Human Rights. The bombs are made of TNT packed into oil drums that are dropped from the air.

- In late July 2014, Human Rights Watch says the number of neighbourhoods hit by barrel bombs has almost doubled in five months, causing almost 1,700 deaths.

Rebel tactics include firing rockets on government-held areas of the city. 

- Russian intervention -- In September 2015, Russia comes to the aid of Assad's government, launching air strikes on Syria.

- February 1, 2016: The regime launches an offensive against rebels in Aleppo province, backed by Hezbollah fighters and Russian aircraft. 

- February 27: A "cessation of hostilities" is declared but it excludes IS and Al-Nusra. Warplanes strike rebel-held areas of Aleppo again on March 11, and a surge in violence in the city kills more than 300 civilians in two weeks from April 22.

- July 17: Government forces cut the rebel's last supply route into Aleppo city, effectively placing east Aleppo under regime siege.

- On September 22, after a one-week ceasefire brokered by Russia and the United States ends, the Syrian army announces a major offensive to retake all rebel-held areas.

- October 24: A three-day unilateral ceasefire declared by Russia ends with only a handful of residents quitting the besieged east.

- On November 4, a similar 10-hour Russia-announced ceasefire ends, marred by rebel fire on evacuation routes and with no sign any civilians or rebels left east Aleppo.

- On November 15, regime forces launch a new assault to recapture the entire city. 

They seize control of all northern rebel-held districts on Monday, sending thousands of desperate residents fleeing.