Syrian government forces have encircled Aleppo, once Syria's most populous city, and with Russian backing, are bombarding it with attack planes and helicopters. Capturing the city would be the biggest victory for President Bashar al-Assad in what has already been a half-decade of war. The current siege, targeting rebel-held areas in the city's east, has been met with fierce resistance from rebel militias.

Pro-government forces have a major advantage in that they have air power that the rebels do not. The shelling from the air is often indiscriminate, but has recently targeted hospitals. Rebels are guilty of their own indiscriminate mortar shelling of government controlled neighborhoods. The rebel groups are numerous, and some are loosely backed by the U.S.-led coalition, while most are not, including the group formerly known until recently as Jabhat al-Nusra, which was affiliated with al-Qaeda.

On Sunday, supporters of the rebels took to the streets. In the absence of a no-fly zone, which none of the major powers operating in Syria has ever come very close to implementing, the supporters tried to make do on their own. Pictures and videos shared by rebel supporters as well as other anti-government activists showed people, including many children, burning tires across eastern neighborhoods in the city.

The dense, black smoke from those fires rose over the bombed-out carcasses of the neighborhood's buildings, and, to a certain degree, may have limited the government planes' capacity to identify targets.

In the video below, a rebel supporter somewhat sarcastically apologizes to "all organizations that protect the environment" for the pollution caused by the fires. But he claims that it is necessary to stop the planes from attacking and to "stop the crimes of the Russians and the Assad regime."

The Syrian and Russian governments jointly announced "safe corridors" through which civilians could leave Aleppo, but very few have enough trust to embark on that journey. Both sides are reported to have made preparations for the siege of Aleppo to last many more days, if not weeks or longer.

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