Under siege

The northern Syrian city of Aleppo has been caught in a four-year deadlock – but that has now been broken.

Aleppo has been a key battleground in the war between forces loyal to President Bashar al-Assad and rebels who want to overthrow him.

Since November, Syrian government forces have rapidly retaken almost all of the opposition-held east, leaving the rebels on the brink of defeat.

Tens of thousands of civilians have fled those districts, but the UN says hundreds have gone missing since crossing into government-controlled areas – and that rebels are preventing some civilians from leaving.

Meanwhile many of those in the areas seized by troops are suffering serious food and fuel shortages.

Why is Aleppo important?

Aleppo was once Syria’s largest city, with a population of about 2.3 million. It was also the country’s industrial and financial centre.

The old city is a Unesco World Heritage site, and was famous for its 13th Century citadel, 12th Century Great Mosque and huge covered markets, or souks.

When the uprising against President Assad erupted in 2011, Aleppo did not see the large protests or the deadly violence that shook other towns and cities.

But it suddenly became a battleground in July 2012.

Rebel fighters launched an offensive to kick out government forces and gain control over northern Syria. But the rebel assault was not decisive.

Aleppo ended up divided roughly in half – the opposition in control of the east, and the government the west.

Over the next four years, the battle for Aleppo became a microcosm of the wider conflict in Syria.

It highlighted the weakness of both sides, as well as the failure of the international community to protect civilians and broker a peace agreement.

• Why Assad wants to take all of Aleppo
• Why is Russia engaged in Aleppo?
• Profile: Aleppo, Syria’s second city

Who has been fighting?

On the government side, state forces are being supported by Russian air strikes and Shia militias, including fighters from Iran, Iraq, Afghanistan, Lebanon and Pakistan.

The predominantly Sunni opposition is made of several rebel groups, many of whom have received financial aid from key opponents of President Assad, including the US, Saudi Arabia and Turkey.

Hardline Islamist groups are involved too, most notably Jabhat Fateh al-Sham, which earlier this year changed its name from the Nusra Front and announced it was cutting ties with al-Qaeda.

How the rebels have lost ground in 2016

4 Jan: At the start of the year, the rebels hold eastern Aleppo, linked to the border with Turkey via territory to the north and west. Turkey’s government is a key backer of the rebellion against Mr Assad.

1 Aug: By August, government forces surround the rebels, taking control of the strategically-important Castello Road in northern Aleppo, the only route into the rebel-held east. About 275,000 people suddenly find themselves under siege.

22 Aug: Rebels and al-Qaeda-linked jihadist fighters in the countryside outside Aleppo seize back control of a route through the Ramousseh district in the south of the city linking them up with the outside world.

17 Oct: Government forces retake the area in early September and resume the siege. There is a brief pause in the offensive in mid-October to allow civilians and rebels to leave, but few take up the offer.

28 Nov: Syrian government forces recapture more than a third of rebel-held territory in eastern Aleppo. The rebels lose all of the northern neighbourhoods, leaving them with under two-thirds of the territory they had in the city.

6 Dec: Troops advance further, seizing more districts in the east. The gains mean the government has now recaptured more than 70% of the rebel-held area.

12 Dec: The Syrian army makes more gains, taking several districts, including the key Sheikh Saeed area, from the rebels, leaving them confined to a small enclave.

13 Dec: Following intense bombardment from pro-government forces, the rebels are squeezed into ever smaller areas of the city, retreating into just a handful of neighbourhoods. Russia’s ambassador to the UN later says that military action has ended in eastern Aleppo.

Syrian government forces launch their final push

After the government resumed its air campaign on 15 November, troops pushed into several northern Aleppo districts and forced rebels and jihadists to retreat southwards. Tens of thousands of civilians fled their homes.

By 13 December, more than 90% of the city had fallen to the government. The UN warned up to 100,000 people were trapped in “ever-shrinking” areas of eastern Aleppo, adding that rebels were stopping people from leaving.

Food and fuel in the city are running out, and basic infrastructure and health care have been obliterated – at one point in November, all hospitals in eastern Aleppo were virtually out of action as a result of air strikes.

The UN says hundreds of civilians have died, but the government and Russia have denied targeting them. Rebel rocket and mortar fire has also killed dozens of people in the government-controlled west.

• Life under siege in rebel-held Aleppo
• Why are people still living in east Aleppo?
• Why are Aleppo’s children so badly affected?

What happens if rebel-held Aleppo falls?

If rebel-held Aleppo is retaken, Syria’s government will control the country’s four largest cities.

President Assad may hope that the gains made in Aleppo will snowball into something more and help bring the civil war to an end.

But with rebel forces, jihadist groups and Kurds still controlling large parts of the country, there would still be a long way to go.

So there is a possibility that it may become a different type of war – with rebels not trying to hold territory and create their own entity, but instead pursuing a hit-and-run insurgency.