President Bashar al-Assad is determined to retake Syria's second city Aleppo to deal a decisive blow to the rebels ahead of a possible change in US foreign policy, analysts say.
Assad's regime has in recent months been pressing a series of offensives to seize control of the devastated city's east, which has been in rebel hands since 2012.
The latest assault made a major breakthrough on Saturday when government forces seized the largest of the city's opposition-controlled neighbourhoods.
For Assad's regime, taking Aleppo would be "one of its greatest victories", Middle East expert Mathieu Guidere says, stressing the city's "extraordinary historical, political and geopolitical prestige".
"It was one of the first cities to be taken by the armed opposition," he adds.
Syria's former economic capital and industrial hub lies at a strategic commercial crossroads near the border with Turkey.
The city has been roughly divided since 2012 into a rebel-held east and a government-controlled west.
Fabrice Balanche, a Syria expert at the Washington Institute for Near East Policy, says the regime retaking east "Aleppo would be a turning point" as it would then control "the five largest cities in Syria".
Assad's forces already control the capital Damascus, the central cities of Homs and Hama and the coastal city of Latakia.
Bringing Aleppo under their control would also give regime forces a better chance at taking back the northwestern province of Idlib, which is almost entirely held by rebels and jihadists.
'Balance of power'
Bassam Abu Abdallah, an analyst close to the Damascus regime, says east Aleppo's fall would "tip the balance of power in the conflict".
Regime forces have since July 17 besieged east Aleppo, where some 250,000 civilians face severe food and fuel shortages and nearly all hospitals have been damaged by bombardment.
"The aim is to push these (rebel) groups towards a scenario like in Homs," Abu Abdallah says, referring to Syria's third city where rebels were defeated in 2014 after two years of regime siege and bombardment.
The current offensive will either lead to a truce or to rebels being evacuated towards other opposition-held areas in Syria, he says.
The latest regime push comes after days of intense bombardment of the east, which has been pounded with air strikes, shells and barrel bombs.
Analysts say the relentless bombing also aims to push war-battered, hungry residents to turn against the armed opposition.
More than 4,000 civilians fled rebel-held districts into regime-held areas this weekend in the first exodus of the kind in east Aleppo since 2012.
Assad's regime "can only take back a territory if its population no longer backs the rebels", Balanche says.
The government regaining control of Aleppo would mark the end of fighting on a major battlefront in a war that has killed 300,000 people since it started in 2011 with the brutal repression of anti-government protests.
Upper hand in talks
Rebels would then control pockets of territory only in the southern province of Daraa, the birthplace of the uprising, and near Damascus where they have lost their previous bastions of Daraya and Moadamiyeh al-Sham.
A defeat in Aleppo would mean rebel groups "are no longer able to maintain the population under their control or protect them", Guidere says.
Balanche says the insurgents losing Aleppo would show the "opposition is incapable of a major military success" and dash its hopes of presenting itself as a viable alternative to the Damascus regime.
Aleppo's fate will be key in any resumption of stalled peace talks to end the five-and-a-half-year war after three failed attempts at UN-brokered dialogue this year.
Guidere says the regime would have the upper hand and "tend to want to negotiate even less" if it seized east Aleppo.
US president-elect Donald Trump taking up office in less than two months' time and a possible subsequent change in American foreign policy could also give Assad the advantage.
If Damascus controls both the capital and Aleppo in January when Trump arrives in the White House, "he may say replacing the regime is categorically out of the question", Guidere says.
Balanche agrees: "We know Trump doesn't really want to invest himself in Syria. If Aleppo falls... it will no longer be worth supporting the opposition."