Militants have seized control of a second major city in Syria in what experts say is a turning point in the country’s 13-year civil war.
The Hayat Tahrir al-Sham (HTS) militant group and its allies captured the key city of Hama on December 5, just days after taking over the country's second city, Aleppo.
The lightning advance is a significant blow to President Bashar al-Assad, who has relied on key allies Iran and Russia to remain in power since the conflict erupted in 2011.
The fall of Hama "illustrates that this offensive has staying power and is not just a blitzkrieg," said Aaron Zelin, a senior fellow at the Washington Institute.
Hama is key to the defense of the capital, Damascus, and the gateway to Syria's coastal cities -- the heartland of the Alawites, the sect of Shi’ite Islam to which Assad and many of his supporters belong. The coast is also home to a strategic Russian naval base and air base.
"It makes it easier [for the militants] to potentially take over Damascus," Zelin said.
Phillip Smyth, an expert on Iranian proxies and Shi'ite militias, said the fall of Hama was a "game-changer," with the militants "demonstrating that the Assad military machinery is a shell."
Still, despite losing two key cities in little over a week, Assad is not yet facing an existential crisis, experts say.
Syrian government forces -- who suffer from low morale and poor pay as well as dysfunction in the chain of command -- still control Homs, the country’s third city, and the capital.
As the militants push further south to "the core territories of the regime," Zelin said, they will face stiffer resistance.
Rebels led by the Islamist militant group Hayat Tahrir al-Sham drive along a street in Rashideen, Syria, on November 29.
Assad has relied heavily on Tehran and Moscow to shore up his forces. But both countries have been distracted by their own crises.
Since 2013, Iran deployed hundreds of Islamic Revolutionary Guards Corps (IRGC) officers to recruit and train tens of thousands of local and foreign Shi'ite fighters.
Russia’s aerial campaigns against rebel positions since 2015 helped the Syrian Army and Iran-backed militias regain swaths of territory.
Moscow is preoccupied with its war in Ukraine. Iran has been focused on other conflicts in the Middle East, including in Lebanon and the Palestinian territories.
The Lebanese armed group Hezbollah, another key player in the Syrian conflict and ally of Damascus, has been severely weakened after a yearlong war with Israel.
SEE ALSO: The Key Players In Syria's Reignited Civil WarMoscow and Tehran have been slow in getting more support to Assad. Russia has intensified air strikes on militant-held areas and Iran-backed Shi’ite militias have headed to the front lines.
But it is unclear if that will be enough to stop the advance of the HTS, a U.S.-designated terrorist organization, and its allies.
"Iran requires air support for its militias and recruits, but Russia is having trouble providing it due to Ukraine," Smyth said.
"Additionally, the Israel-Hamas-Hezbollah war had been extraordinarily costly for Iran's command and control apparatus in Syria that relied on Hezbollah. It will be a slower-burning process than before."