Who are Hayat Tahrir al-Sham, the rebels taking control of Aleppo?

Rebel forces launched their biggest offensive against the Syrian government in years on Wednesday.

By Saturday, they had taken over “large parts” of the country’s second largest city, Aleppo.

The surprise offensive prompted Russia’s first strikes on Aleppo since 2016 and saw the Syrian army withdraw its troops from the city.

The attack was led by the Islamist militant group Hayat Tahrir al-Sham (HTS) – which has a long history of involvement in the Syrian conflict.

HTS was established under another name, Jabhat al-Nusrain 2011 as a direct affiliate of Al Qaeda.

ISIS leader, Abu Bakr al-Baghdadiwas also involved in its formation.

It was considered one of the most effective and deadly of the groups against President Assad.

But his jihadist ideology appeared to be his driving force rather than revolutionary zeal – and he was seen at the time as being at odds with the main rebel coalition under the Free Syria banner.

But in 2016, the group’s leader, Abu Mohammed al-Jawlani, publicly broke ranks with Al Qaeda, disbanded Jabhat al-Nusra and established a new organizationwhich took the name Hayat Tahrir al-Sham when it merged with several other similar groups a year later.

The war in Syria has looked for the past four years as if it were effectively over.

President Bashar al-Assad’s rule is essentially unchallenged in the country’s major cities, while other parts of Syria remain outside his direct control.

These include Kurdish-majority areas in the east that have been more or less separated from Syrian state control since the early years of the conflict.

There has been some ongoing, albeit relatively mild, unrest in the south where the revolution against Assad’s rule began in 2011.

In the vast Syrian desert, holdouts by the self-proclaimed Islamic State group still pose a security threat, particularly during the truffle hunting season, when people flock to the area to find the highly lucrative delicacy.

And in the northwest, Idlib province was held by jihadist and rebel groups led there at the height of the war.

The dominant force in Idlib is the one that launched the surprise attack on Aleppo, HTS.

For several years, Idlib remained a battleground as Syrian government forces tried to regain control.

But a ceasefire agreement in 2020 brokered by Russiawhich has long been Assad’s key ally, and Turkey, which has backed the rebels, has largely held its own.

About four million people live there – most of them displaced from towns that Assad’s forces won from rebels in a brutal war of attrition.

Aleppo was one of the bloodiest battlefields and one of the biggest defeats for the rebels.

To achieve victory, Assad relied on Russian air power and Iranian military aid on the ground – mainly through Iranian-sponsored militias.

These included Hezbollah.

There is no doubt that the recent setback Hezbollah has suffered Israel’s offensive in Lebanonas well as Israeli attacks on Iranian military commanders in Syria, played a significant role in the decision of jihadist and rebel groups in Idlib to make their sudden and unexpected move to Aleppo.

For some time now, HTS has established its power base in Idlib, where it is the de facto local government, although its efforts at legitimacy have been dogged by alleged human rights abuses.

He was also involved in some infighting with other groups.

His ambitions beyond Idlib had become unclear.

Since breaking with Al Qaeda, its focus has been limited to trying to establish fundamentalist Islamic rule in Syria, rather than a wider caliphate, as Isis tried and failed to do.

It had shown little sign of trying to reignite the Syrian conflict on a major scale and renew its challenge to Assad’s rule over much of the country — until now.

Additional reporting by Maia Davies.