Syria's revived insurgency: All you need to know

Militants have taken control of large parts of the north-west, forcing government troops to withdraw

People inspects a camp for internally displaced people destroyed during an air strike near the village of Harbnush, north of Idlib, Syria. AP

People mourn relatives killed in a reported Syrian regime air strike on Wadi Khaled camp at the SAMS Hospital in Maarat Misrin, a town in Syria's northern Idlib governorate. AFP

Displaced Syrian Kurds ride in the back of a vehicle loaded with belongings on the Aleppo-Raqqa motorway to flee areas on the outskirts of the northern city of Aleppo after they were seized by Islamist-led rebels. AFP

Medics inspect the damaged Ibn Sina Hospital following a Russian air strike, in Idlib, northern Syria. EPA

Militants gather at the Nayrab military airport, in the northern Syrian city of Aleppo. AFP

Syrian military aircraft are among the equipment at the airport. Militants have taken control of large parts of Aleppo. AFP

A militant patrols outside the airport. The offensive has resulted in Russian air strikes on Syria. AFP

Fighters stand guard outside the northern Syrian town of Tal Rifat. AFP

A member of the Syrian White Helmet civil defence helps carry a victim of Syrian government attacks on Idlib city. AP

Anti-government fighters reach the motorway near the northern Syrian town of Azaz. AFP

Anti-government fighters celebrate as they take over the northern Syrian town of Tal Rifaat. AFP

Anti-government fighters swept into the city of Aleppo, east of Idlib province. AFP

The Syrian army said dozens of its soldiers had been killed in the attack on Aleppo. AFP

Smoke billows in the aftermath of what the White Helmets say is a strike, in Idlib, Syria. Reuters

Syria's President Bashar Al Assad meets Iran's Foreign Minister Abbas Araghchi, in Damascus. Reuters

A nurse attends to an injured woman in Idlib, Syria. Government air strikes in Idlib killed at least three civilians, including two children, and wounded 11 others, said the Syrian Civil Defence. AP

Anti-government fighters take a position near the northern Syrian town of Tal Rifaat. AFP

Anti-government fighters ride a motorcycle in the northern Syrian town of Tal Rifaat. AFP

People cross an anti-government checkpoint as they return to the town of Saraqib in the eastern part of Idlib province. AFP

Syrian opposition fighters seize abandoned Syrian army ammunition in the town of Khan Assubul, Syria, southwest of Aleppo. AP

Militants in Syria led by Hayat Tahrir Al Sham launched a surprise attack in Aleppo last week, taking control of large parts of the city and advancing south towards Hama. The insurgency prompted Syria's military to withdraw from the city and led to the first Russian air strikes on Aleppo since 2016.

Militant groups withdrew after the Syrian army regained control of the north-western city eight years ago, with the support of Iran’s Islamic Revolutionary Guard Corps, as well as Tehran-backed Hezbollah and a Russian air campaign. Since then, the government has remained in control of the majority of the country.

The offensive began on Wednesday, with militants sweeping through villages outside Aleppo. They had seized large areas of the city by Saturday and now claim to have taken control of parts of the Hama and Idlib provinces, in the west and north-west of Syria.

The Syrian civil war, which the UN says has killed more than 300,000 people, forced 14 million to flee their homes in search of safety. More than 7.2 million Syrians remain internally displaced. About three years after the conflict began, ISIS rose up to take over about a third of Syria and 40 per cent of Iraq, prompting western countries including the US to launch an international coalition to eliminate the terrorist group.

What began 13 years ago as pro-democracy protests against the government of President Bashar Al Assad, grew into a nationwide armed rebellion involving a coalition of militias and Islamists groups. It had been stagnant in the past couple of years, after Russia and Turkey agreed to a ceasefire in 2020 in Idlib.

But there are fears the renewed conflict raging in Syria could further destabilise the region at a time when Israel continues to wage a crushing war on Gaza.

Who is leading the militant offensive?

Hayat Tahrir led the attack in Aleppo. It was mainly made up of groups from Jabhat Al Nusra, which was linked to Al Qaeda. The group broke those ties in 2016 and rebranded itself as Hayat Tahrir.

The UN and countries including the US, Russia and Turkey have long designated it as a terrorist organisation. Its leader Abu Mohammed Al Jolani participated in the Iraqi insurgency against the US as a member of the group that eventually became ISIS. He led the Syrian branch of Al Qaeda in 2011, in the early years of the civil war.

Hayat Tahrir is considered to have played a significant role in the Syrian civil war, but its extreme ideologies and acts of violence against civilians puts it at odds with moderate opposition groups.

Who are the other players?

Militant groups include factions supported by different regional and local powers, making Syria one of the most complex front lines in the Middle East.

In addition to the fighting in Aleppo, another battle front is led by the Turkey-backed Syrian National Army – the violence is mainly between Kurdish fighters in Syria with links to the People's Defence Units (YPG) and Kurdistan Workers' Party (PKK), a group that has waged a decades-long insurgency in Turkey. The UK-based Syrian Observatory for Human Rights has said pro-Turkey fighters have taken control of the northern town of Tal Rifat and several other villages.

Meanwhile, the Syrian Democratic Forces (SDF), dominated by Kurdish fighters from the YPG, were a dominant force in fighting against ISIS in north-eastern Syria. The US has about 900 troops in north-east Syria, in what it says is an operation to curb the terrorist group. The US and Israel have conducted strikes on Syria, with civilians among those killed.

Who supports the Syrian government?

Russia has been a staunch supporter of Mr Al Assad and has launched air strikes against rebel forces in Aleppo and Idlib during the civil war. Russian warplanes have been critical for the Syrian government in winning back territory. Mr Al Assad has vowed that Syria will continue “to defend its stability and territorial integrity”.

Iran is also a close ally and backer of Mr Al Assad, with proxies such as Hezbollah playing a crucial role in the civil war. Iranian Foreign Minister Abbas Araghchi met Mr Al Assad in Damascus on Sunday and said Tehran would “firmly support the Syrian government and army".

Why is the timing of the offensive crucial?

The militants have chosen to launch the insurgency when Mr Al Assad’s key allies are either weakened or occupied with other conflicts. The offensive began soon after a ceasefire was reached between Israel and Hezbollah in Lebanon. But Israel's assault on Lebanon has weakened Hezbollah and put Iran on the back foot.

Russia has focused military resources in Ukraine, where the war has been raging for more than two years.

“Keep in mind that, for many years, the Syrian government has been engaged in a civil war backed by three main players, Iran, Russia and Hezbollah,” US National Security Adviser Jake Sullivan said on Sunday. "All three of those players have been distracted and weakened by conflicts elsewhere."