ALEPPO, Syria -- The sniper walked through the rubble near this city's front lines. He was searching for another spot from where he might catch a Syrian soldier in his rifle scope's cross hairs.
Speaking in French-accented English, he said he was not Syrian, but a roaming jihadist who had journeyed here to help the Sunni uprising against President Bashar al-Assad's secular, Alawite rule.
"I am a Muslim," he said. "When you see on TV many of your brothers and sisters being killed you have to go help them. This is an obligation in Islam."
The presence of this foreign antigovernment fighter, who claimed to be from Paris and gave his name as Abu Abdullah, pointed to recurring questions of the battle for Syria's largest city: How much longer will the fighting last, and what will its effects be?
Now in its sixth month, the battle for Aleppo has become the contest for Syria in a microcosm, exposing the weakness of both sides, while highlighting anew the perils and costs of the country's bitter civil war.
It has underlined the rebels' difficulties in organizing a coherent campaign; their paucity of infantry weapons heavier than machine guns; and some of their fighters' participation in the same human rights abuses for which they condemn the government, including the summary killing of prisoners.
It has also left rebels vulnerable to allegations of corruption, including the theft of much needed food and other aid.
Simultaneously, the fighting has exposed the government's seemingly fatal miscalculations. For all of its statements to the contrary, and no matter its effort to mass soldiers and firepower here, Mr. Assad's government has mustered neither the popular support nor the military might to stop the rebels' slow momentum, much less to defeat them.
These days rumors circulate of Mr. Assad's dilemma -- will he flee Damascus, Syria's capital, or die behind the palace gate? -- while it is rebels who speak with confidence.
"Now we are making very good progress," said Col. Abdul Jabbar al-Okaidi, a former Syrian military officer who is now one of the senior rebel commanders in the Aleppo region. "Almost all of the military bases and regime forces in Aleppo have been surrounded."
As winter descends, intensifying the humanitarian crisis for Aleppo's civilians, the battle's direction has decisively shifted.
The Syrian Army units here have been largely cut off from the capital. For weeks they have been yielding ground, contracting under the pressures of persistent rebel attacks from almost every direction and the related difficulties of resupply.
The military's tactic of collective punishment -- manifested through seemingly indiscriminate airstrikes and artillery barrages on residential neighborhoods -- has earned it only anger and disgust.
One opposition activist noted the army's practice of firing a few artillery rounds into neighborhoods, waiting five or ten minutes for civilians to gather to help the wounded, and then firing again -- resembling NATO's practice of repeat airstrikes in its campaign in 2011 to unseat Col. Muammar el-Qaddafi of Libya. "Sometimes we wait and don't go out after the first shells, because we know other shells are coming," said the activist, Mumtaz Mohammad. "There are a lot of victims who were killed because of this policy."
Once able to roam freely in its armored columns, the army begins the winter confined mostly to the city's south and west. It also retains tenuous control of the airport in the southeast, although rebels have pushed close to its fences and claim to have positioned many antiaircraft weapons there.
Syrian Air Force support, almost continuous in the city over the summer, has dwindled. The sound of Russian-made helicopters, once constant, is now unusual.
Passing attack jets often dispense bright strings of decoy flares -- a sign that pilots fear the rebels' portable, heat-seeking missiles, used to shoot down at least one aircraft late in the fall.
But these accumulating rebel successes have not come without setbacks, costs and questions about Syria's future. The army, while weak, is still potent and difficult to dislodge where it has concentrated forces in Aleppo, just as it has done in most of Syria's cities.
On one recent day, rebels gathered at their front-line posts near the Hanano military base. The rebels had captured the base in the summer, only to lose it to an army counterattack, apparently after the rebels left too light a guard and failed to consolidate their gains.
Now the rebels tried to retake what they had held, pressing within 65 yards of their enemies via a warren of alleys.
In one street, the corpse of a Syrian soldier lay in the rubble. Both sides watched over the body, since neither could venture into the daylight to retrieve it without drawing fire.
One front-line commander, Mohammad Bakkar, 36, said he had been drawn almost unwillingly into his life as an urban guerrilla.
"The regime considered almost every grown man who was not on their side to be a wanted man," he said. "They started visiting my house, asking about me. They left a note telling me to come visit them at the intelligence department."
"Instead I joined the Free Syrian Army," he said.
Mr. Bakkar, like others, spoke of returning to a peaceful life after Mr. Assad's defeat.
But these men also said that the army could prove even more dangerous in its decline. Cornered units, knowing that rebels have killed prisoners, might fight until death. And there have been ample signs throughout the year that the government has exercised less restraint as rebels have grown stronger.
(Colonel Okaidi said that rebels often try to take army positions piecemeal, hoping, as they advance, to persuade soldiers to surrender.)
The fighters and opposition activists also said that Syria's population has been altered by the war, and is now more sectarian, more religious, much more armed and deeply disappointed, often outraged, at the inaction by the West.
The presence of foreign fighters like Abu Abdullah, and the calls for religious law that have been heard in many places across rebel-held territory, have left many to say that the fall of Mr. Assad, even if the day came soon, would signal the end of one phase of the war, and perhaps the start of another. In this way, Aleppo offered a glimpse.
Abu Abdullah, for his part, wandered the front with unmistakable approval of the Syrian fighters around him. With dreadlocks protruding beneath his black watch cap, he slung his Dragunov-style rifle and surveyed the broken buildings, looking for an elevated spot from which to watch the army positions near Hanano, waiting for a soldier to become a target.
He said that he had fought in Pakistan and Afghanistan and suggested that he had been a sniper in Iraq. Now, he said, it was Syria's turn at war, which mixes an uprising against a repressive government with the older, uglier contest between Sunnis and Shiites. His mission suggested he saw no quick end to the violence. "I am here," he said, "to teach the Syrians to snipe."world
This article originally appeared in The New York Times.