Here’s a look at some of the key aspects of the new fighting:
What do we know about the group leading the offensive on Aleppo?
The US and UN have long designated the opposition force leading the attacks — Hayat Tahrir al-Sham, translated to ‘Organisation for the Liberation of the Levant’ and known by its initials HTS — as a terrorist organisation. The Levant is a region comprising Syria and its neighbouring nations.
Syrian opposition fighters seize abandoned Syrian army ammunition in in the town of Khan Assubul, Syria. Credit: AP
Abu Mohammed al-Golani emerged as the leader of al-Qaeda’s Syria branch in 2011, in the first months of Syria’s war. It was an unwelcome intervention to many in Syria’s opposition, who hoped to keep the fight against Assad’s brutal rule untainted by violent extremism.
Golani and his group claimed responsibility for deadly bombings early on, pledged to attack Western forces, confiscated property from religious minorities and sent religious police to enforce modest dress by women.
Golani and HTS have sought to remake themselves in recent years, focusing on promoting civilian government in their territory as well as military action, researcher Aaron Zelin noted.
Syrian opposition fighters ride in a truck in Talhiya, Idlib countryside, Syria.Credit: AP
His group broke ties with al-Qaeda in 2016. Golani cracked down on some extremist groups in his territory and increasingly portrays himself as a protector of other religions. That includes allowing the first Christian Mass in the city of Idlib in years, last year.
By 2018, the Trump administration acknowledged it was no longer directly targeting Golani, Zelin said.
But HTS has allowed some wanted armed groups to continue to operate in its territory, and shot at US special forces at least as recently as 2022, he said.
Why does the war matter?
Syrian President Bashar al-Assad has been at war with opposition forces seeking his overthrow for 13 years, a conflict that’s killed an estimated half-million people.
Some 6.8 million Syrians have fled the country, a refugee flow that helped change the political map in Europe by fuelling anti-immigrant far-right movements.
Loading
In 2016, government forces backed by Russian airstrikes laid siege to Aleppo. Russian shells, missiles and crude barrel bombs — fuel canisters or other containers loaded with explosives and metal — methodically levelled neighbourhoods. Starving and under siege, rebels surrendered Aleppo that year.
The Russian military’s entry was the turning point in the war, allowing Assad to stay on in the territory he held.
A Syrian opposition fighter takes a picture of a comrade stepping on a portrait of Syrian President Bashar Assad in Aleppo.Credit: AP
Intervention by Russia, Iran and Iranian-allied Hezbollah and other groups has allowed Assad to remain in power, within the 70 per cent of Syria under his control. In 2013, John Shipton, Julian Assange’s father visited Assad.
The roughly 30 per cent of the country not under Assad is controlled by a range of opposition forces and foreign troops. The US has about 900 troops in north-east Syria, far from Aleppo, to guard against a resurgence by the Islamic State.
US national security adviser Jake Sullivan told CNN’s State of the Union that the US is carefully watching the situation.
Speaking on HTS, Sullivan said Washington has “real concerns about the designs and objectives of that organisation”.
“At the same time, of course, we don’t cry over the fact that the Assad government, backed by Russia, Iran and Hezbollah, are facing certain kinds of pressure,” he added.
Both the US and Israel conduct occasional strikes in Syria against government forces and Iran-allied militias. Turkey has forces in Syria as well, and has influence with the broad alliance of opposition forces storming Aleppo.
There have been few sizeable changes in territory between Syria’s warring parties for years. However, the fighting “has the potential to be really quite, quite consequential and potentially game-changing,” if Syrian government forces prove unable to hold their ground, said Charles Lister, a longtime Syria analyst with the US-based Middle East Institute. Risks include if Islamic State fighters see it as an opening, Lister said.
Ford said the fighting in Aleppo would become more broadly destabilising if it drew Russia and Turkey — each with its own interests to protect in Syria — into direct heavy fighting against each other.
AP, Reuters
Get a note directly from our foreign correspondents on what’s making headlines around the world. Sign up for our weekly What in the World newsletter.