Antigovernment fighters brandish their guns as they ride a vehicle in Syria's northern city of Aleppo on Nov. 30.

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Antigovernment fighters brandish their guns as they ride a vehicle in Syria's northern city of Aleppo on Nov. 30. / AFP

LONDON — The rapid military advance of a Syrian rebel group this past week has dramatically shifted the frontlines and upended long-held assumptions about a Middle East conflict that appeared stuck in a stalemate.

The group behind these dramatic developments, Hayat Tahrir al-Sham (HTS), has held a consequential but checkered role in the country's long-running civil war.

With its roots in the early days of Syria's 2011 uprising, the Organization for the Liberation of Greater Syria swept down this week from its strongholds in the northwest countryside to take control of a vast swath of a country that had long been under the grip of Syrian President Bashar al-Assad's forces.

HTS surprised many people — including themselves — when they seized control of Aleppo, the country's second largest city, with minimal opposition from government forces.

They have subsequently pushed farther south in the past two days, heading toward the capital Damascus as fighting has broken out in a number of towns and cities across the country.

"We succeeded in breaking the first line and then the second and third," said Gen. Ahmed Homsi, the commander of a unit that's been trying to coordinate the rebel offensive, during an interview with NPR.

"We hit positions of the leadership and succeeded in cutting off communications between them and their troops. That created big chaos for them. It was a big psychological defeat."

A billboard bearing a picture of Syria's President Bashar al-Assad and a national flag are torn by antigovernment fighters in the northern city of Aleppo on Nov. 30.

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A billboard bearing a picture of Syria's President Bashar al-Assad and a national flag are torn by antigovernment fighters in the northern city of Aleppo on Nov. 30. / AFP

HTS has transformed repeatedly over the years since the Syrian civil war began in 2011, with name changes, personnel splits and an expanded role in the country's northwest province of Idlib, where it has largely governed undisturbed for several years.

An Islamist group that the US and several other nations long ago designated a terrorist organization, it was known as Jabhat al-Nusra when it formed a formal alliance with Al-Qaida more than a decade ago.

But in recent years HTS has publicly disavowed international terrorism and tries to present a more moderate face, according to Charles Lister, the director of the Syria Program at the Middle East Institute think tank in Washington D.C.

"The group has completely turned away from having any kind of global agenda. It has turned national," Lister says. "But unquestionably, the group retains very conservative religious foundations."

At the moment, HTS leaders say they have no plans to apply Sharia law in areas they control and have even started working with Syria's minority Christian communities, allowing them to rebuild churches and returning their dispossessed lands.

In Idlib province, along the border with Turkey, the group's largely technocratic administrators, known as the 'Salvation Government,' have cooperated with United Nations aid agencies and other international organizations seeking to support the millions of Syrians living there, many of them displaced from other parts of the conflict-ridden country.

Alex McKeever, a researcher with the organization Syrians for Truth & Justice, says Turkey's support for the group has also been crucial - even though it was originally intended just to fend off government forces.

"One of Turkey's main policy goals in Syria since 2016 is to prevent a further influx of refugees across the border into Turkey," says McKeever, who is based in the Jordanian capital of Amman, and the Turks were convinced that a flood of fresh migration "would most likely be caused by a regime offensive that manages to take the entire Idlib pocket."

All that international assistance, proximity to the border and cooperation with other rebel groups elsewhere in Northern Syria has allowed HTS to develop a diversified economy, says Caroline Rose, a senior fellow at the New Lines Institute think tank. It's a model that Rose says HTS may seek to replicate elsewhere.

"It strives not only to retain but also set up proto governance in Aleppo city and the areas around it, eventually establishing a monopoly over not only local territory, but also goods and services for taxation, much like what we've seen in Idlib in the northwest."

An aerial view shows people crossing an antigovernment checkpoint as they return to Saraqib in the eastern part of Idlib province in northwestern Syria on Dec. 1.

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An aerial view shows people crossing an antigovernment checkpoint as they return to Saraqib in the eastern part of Idlib province in northwestern Syria on Dec. 1. / AFP

And that need to govern millions of people has really transformed the group, according to former U.S. Ambassador to Syria Robert Ford.

"It's not what it was," Ford says. "It's not what I had imagined when we pushed to get them on the terrorism list in 2012. Back then they were 'al Qaeda in Iraq, Syria branch.'"

Another significant evolution for HTS is its decision to collaborate with other armed Syrian factions, against which it might previously have fought, says Lina Khatib, an associate fellow in the Middle East and North Africa program at Chatham House

"After years of battles and competition with other rebel groups, HTS has now built an alliance of convenience with those groups," says Khatib. "This is an alliance against Iran backed militias and against the forces of the Syrian regime of Bashar al-Assad." 

But as HTS celebrates its relatively easy advance, the Syrian army and its Russian- and Iranian-backed allies are preparing to fight back. That will mean holding even more new territory — let alone one day governing it — may prove much more difficult for the group and other armed factions fighting alongside them, says Jerome Drevon, a senior analyst on Jihad in Modern Conflict at the International Crisis Group.

"They have really restructured themselves over the past few years, they've become more professional," Drevon says. "The issue is, if you try to expand further elsewhere, then you know they would spread thinner, and command and control might be a bit more difficult to maintain over these groups if they go to the south."

Lama Al-Arian contributed reporting from Beirut.