Damascus has been surrounded by a semicircle of hostile neighborhoods, according to activists and military analysts, where rebels have assembled enough weapons and men to overrun air force and military bases around the capital. Their stronghold, from the northeast to southwest suburbs of Damascus, is bisected by a major lifeline for the regime: the Damascus International Airport.

While the airport and the highway leading to it still seem to be under government control, rebels are attempting to choke off that major artery linking the capital to the world. Rebel groups say they have fired mortars into the airport, effectively rendering the facility unsuitable for commercial traffic, and have besieged the airport from three directions. The video below shows some of their positions.

As a relative safe haven from much of the extreme violence in Syria, Damascus has taken in hundreds of thousands of internally displaced Syrians since government tanks stormed Daraa in April 2011 and war spread across the country. But this time around the refugees have nowhere else to go. Residents feel trapped, says a civil engineer who lives in the Kafar Souseh neighborhood in the capital. Yet many, including him, are unwilling to leave.

“I’m staying until they shell my house,” he told Syria Deeply. He says his district is relatively safe, given its proximity to multiple security offices, but that it will likely become a battleground as rebels inch closer to the heart of the Assad regime. The city is tense and living conditions are deteriorating every day.

This isn’t the first battle for Damascus over the course of Syria’s war. Rebels entered the city in July and sparred with the regime in many central neighborhoods, but their weapons and tactics were no match for the helicopter gunships and elite soldiers defending the capital. The government was able to regain control and push back the fight to the city’s suburbs.

This time, the rebel offensive is strategically different. Opposition fighters have organized themselves, establishing better command structures and more resilient supply lines. Since the last fight, they have acquired heavier weapons, including anti-aircraft missiles and some tanks. The Assad regime, on the other hand, has suffered a series of setbacks, seemingly losing large military bases around the country and effectively retreating from vast territories in the north and east.

Losing Damascus doesn’t appear to be an option for the Assad regime. Government troops were recalled from Daraa and the Golan heights over the summer to bolster defenses of Damascus and more units moved into the capital in recent weeks to man hundreds of checkpoints inside the city. The army has installed artillery on the Qassioun mountain overlooking Damascus and has launched multiple rockets from a military airport near the presidential palace (below), which suggests both the overwhelming fire that the regime possesses and its reluctance to use troops to defeat the rebels.

The regime has painted a more optimistic analysis of events, with the pro-government daily Al Watan reporting that the Syrian army “has completely opened the gates of hell before all who would even consider approaching Damascus or planning to attack it.” But its version of events can hardly be trusted.

When rebels swept into Aleppo in July, Al-Watan dubbed the fight as the “mother of all battles,” and predicted that “Aleppo will be the last battle waged by the Syrian army to crush the terrorists and, after that, Syria will emerge from the crisis.” The regime doubled down on Sep. 4, 2012, when the AFP quoted the army’s top commander in Aleppo saying that “in 10 days we will clean Aleppo.” That “cleansing” never happened, and so many are bracing for a long battle in Damascus.

Barring high level defections or a negotiated end to the conflict, the battle for Damascus is expected to continue until one side is victorious, raising fears of more death and destruction in one of the world’s oldest cities. The implications of this critical fight for the capital are already felt outside of Syria, through the increased urgency in diplomatic maneuverings and in the analysis of experts who no longer consider Assad as the absolute ruler of the country.