Rebel fighters from the Free Syrian Army fire a heavy machine gun during a battle against government forces in Aleppo. (KARAM AL-MASRI/AFP/Getty Images)

To the extent that Syria’s leaderless revolution has any leaders at all, Aleppo’s Abdul Qader Saleh was one of them, perhaps the only figure to have emerged from the chaos of the uprising who could claim a broad and genuine following.

His death over the weekend from injuries sustained in a government airstrike came as a bitter blow to a rebel force struggling to hold its own, not only against a reinvigorated government army but also the growing challenge posed by al-Qaeda-linked radicals.

As the military leader of the Tawheed Brigade, the biggest rebel battalion in the northern province of Aleppo, Saleh oversaw at least 10,000 men, making him one of the most powerful military commanders in the country. He had also emerged as its most potent leader.

A warlord who wore a hoodie and walked with a slouch — unlike some of his more swaggering peers — he was not without critics. But he was also a charismatic figure who seemed to inspire a level of devotion among his supporters that has been rare in the ranks of the chronically divided opposition.

As tributes to his heroism and humility flooded Twitter and YouTube, opposition supporters in Aleppo fretted about what may follow now that his unifying presence is gone. “Any defection might happen, or the brigade could even collapse after the shock of his departure,” said Rifai Rifaat, an Aleppo journalist. “Or the same shock might strengthen the brigade, which is carrying the biggest burden of the current battles in Aleppo.”

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Saleh’s death could hardly have come at a more difficult time. The rebels are suffering setbacks nationwide, and the capture of the strategic town of Safira last month by forces loyal to President Bashar al-Assad signaled rebel vulnerability in the one part of the country where it was assumed they were secure.

The setbacks, accompanied by a surge of rebel infighting, prompted the resignation this month of another key Aleppo military leader, Col. Abdul Jabbar Akaidi, whose rivalry with Saleh was renowned. Akaidi hailed Saleh on Monday as “an icon of the revolution, a role model that is rarely seen” and described the slain leader as “a friend and dear brother.”

“At a time when the Syrian regime is advancing on Aleppo, Saleh’s death therefore is very bad news for the opposition,” wrote Aron Lund, an analyst based in Sweden. “Even if the front holds, Tawhid could be drained of cohesion, and end up losing subunits and fighters to other groups.”

Saleh was also a key figure in an ongoing effort to bring greater national cohesion to the rebels by uniting the bigger Islamist brigades under a single umbrella. Though a devout and conservative Muslim, he was regarded as a moderate who bridged the expanding gulf between the original revolutionary goals and the more radical form of Islamism accelerating through the rebels’ ranks as they lose hope of ever receiving Western support.

Some of the laments posted online reflected the sense of wider loss.

“Abdul-Qader Saleh is our revolution, his face is its beauty, and his blood its hope and its light,” an activist called Diana al-Jabri wrote on her Facebook page.

Indeed, his death marked a watershed of sorts. At a time when attention is focusing on beheadings, lashings and other outrages perpetrated by al-Qaeda-affiliated groups and the foreign jihadis who lead them, Saleh seemed to symbolize an earlier era of the war.

A prosperous agricultural merchant in the small, rural town of Marae, Saleh was one of the earliest leaders of the protest movement that erupted in March 2011 among ordinary Syrians seeking new freedoms from a regime they had endured for 40 years.

After the demonstrations failed and the opposition took up arms, he was among the fighters who surged into the city of Aleppo in July 2012, the biggest rebel offensive of the war. Nicknamed Haji Marae after his home town, he was one of the founding members of the Tawheed Brigade, formed to bring unity to an assortment of armed groups, and he quickly won widespread recognition, sleeping with his troops on the ground, regularly visiting the front lines and scrupulously attending to the well-being of his men.

In one famous incident captured on YouTube, he barely flinched as warplanes struck nearby, declaring: “Nobody dies until God gives him his life and his date of death.”

Saleh’s critics point out that he did little to rein in the banditry and looting that marred the first months of rebel control in Aleppo; the chaos helped build support among frustrated ordinary residents for rival Islamist groups. Saleh seemed more focused on military strategy and taking care of his men than on forging the wider political alliances that might have helped avoid the disarray that is now threatening the rebels’ military gains.

An alliance struck with the al-Qaeda-affiliated Jabhat al-Nusra in September raised eyebrows, though other rebel officials say that was spearheaded by Tawheed’s top leader, Abdul-Aziz Salameh, who is considered more radical than Saleh. Salameh will retain overall command of the movement while another military leader is sought to fill Saleh’s place, said one of Saleh’s former aides and relatives.

Saleh also had enemies. He was struck by a sniper’s bullet while standing on a balcony during a failed assassination attempt. The airstrike that killed him Thursday may also have been deliberate; the entire top leadership of the Tawheed Brigade was meeting at a captured military base outside the city when regime warplanes struck, suggesting that the time and location of the gathering had been betrayed to the government, his aides said.

Saleh, badly injured, was rushed to a hospital in Turkey but did not survive. He was buried without fanfare in Marae on Sunday, to avoid further targeting before news of his death spread Monday.

Ahmed Ramadan contributed from Beirut to this report.