Beirut - Syria's largest city has been under siege since government forces shut down Castello Road - a bombed-out gauntlet that for months served as the lifeline in and out of rebel-held eastern Aleppo.
Last week, Kurdish People's Protection Units (YPG) fighters clashed with rebels near the road, contributing to a rebel retreat from the Bani Zaid district and further tightening the siege. Supporters of the YPG say they are protecting northern Aleppo's Kurdish-majority neighbourhood of Sheikh Maqsoud, while critics accuse them of aiding the Syrian government in besieging a city that has become a symbol of Syria's uprising.
For months, Sheikh Maqsoud has formed a key strategic pressure point for the various groups battling for the elusive upper hand in Aleppo - Kurds, rebels and the government.
Abdulkafi al-Hamdu, an activist and English professor at the University of Aleppo, blamed both the government and the YPG for tightening the noose around rebel-held eastern Aleppo.
"We are completely surrounded. We can [only] find food and medicine at very high prices, and that's gotten [even] worse because Castello Road has been besieged by the Assad regime," Hamdu told Al Jazeera. "Kurdish troops [also] took part in surrounding Aleppo by shooting people from Sheikh Maqsoud. We are facing a life which is closer to death."
YPG spokesman Redur Xelil denied that Kurdish fighters have put pressure on the area around Castello Road, blaming the "Free Syrian Army and Islamic brigades" for reneging on temporary agreements and attacking civilians.
As rebel-held Aleppo fights for survival, Sheikh Maqsoud has become an increasingly vital piece of land for Kurdish groups in the city's north. Once loosely considered part of "Free Aleppo" after the uprising against President Bashar al-Assad's government, Sheikh Maqsoud was later gripped by protests and state crackdowns - until the Syrian government effectively ceded control to the Kurdish Democratic Union Party (PYD), Syria's ideological affiliate of the Turkey-based People's Workers Party (PKK), by withdrawing from Kurdish areas in northern Syria in 2012.
Since then, the neighbourhood has been under the control of Kurdish forces, particularly the YPG.
Michael Stephens of the Royal United Services Institute think-tank in London, said that although Sheikh Maqsoud might appear anomalous or strategically isolated on a map, for the PYD it has become "absolutely integral to everything they're trying to do in Rojava", the Kurdish name for the self-declared autonomous region in northern Syria.
Stephens said that Sheikh Maqsoud has been ideologically integrated into the Kurdish project in the north, often mentioned in the same breath as the already self-governing cantons in Afrin and Kobane.
"Clearly it's not an essential frontline. But it's not about that," Stephens said. "It's a unifying front in which people from all across Kurdistan can say, 'Yes, this is a place where Kurds are suffering … This is integral to our identity, national defence, our sense of nationhood.' And you have a larger goal from the PYD: to build an autonomous state."
PYD leader Saleh Muslim has previously stated that the Kurdish project of self-rule in northern Syria could be launched "in a very small town, a very small village, or in the biggest cities ... [The Kurds] could make this project for wherever they are. The Kurds in Damascus could do this for themselves in Damascus. They could be free in Damascus or even in Sheikh Maqsoud."
Robert Lowe, deputy director of the Middle East Centre at the London School of Economics, has researched Kurdish political movements for years and says it is "credible" that the PYD might try to incorporate Sheikh Maqsoud, even though "there are huge issues to surmount if they're to achieve it.
"It's credible that the PYD are looking or exploring how they might incorporate Sheikh Maqsoud into their 'experiment', for want of a better word," Lowe told Al Jazeera, noting that by deftly filling Syria's political vacuum after 2012, the PYD has already exceeded expectations about what it can achieve.
Xelil refused to answer Al Jazeera's questions about the link between the YPG's control of Sheikh Maqsoud and alleged Kurdish state-building in Syria, but said: "The YPG fighters [there] are Sheikh Maqsoud's sons. They have a right to defend their area."
Not everyone from Sheikh Maqsoud agrees. Marouf, an anti-government activist who moved to rebel-held Aleppo and spoke to Al Jazeera on condition of withholding his last name, said that the PYD and YPG "repress Sheikh Maqsoud [through arbitrary detentions and forced disappearances] so that they are the dominant force there".
While debate continues around the PYD's intentions in Sheikh Maqsoud, the YPG's actions in Aleppo have angered rebel groups who accuse the Kurds of using Syria's uprising and war for their own interests: the partition of Syria and the establishment of a Kurdish state in the north. They claim the YPG is willing to side with anyone - Assad included - in their pursuit of self-determination.
"We know they're expanding the Kurdish project, and that must make others in the north who don't back it - or who aren't even Kurdish - quite nervous," Lowe said. "Ultimately, nobody there [in northern Syria] really likes the prospect of the Kurds having control, so they're going to fight it."
As a result, relations between rebel and Kurdish groups have soured to the extent that fighting in Sheikh Maqsoud continued despite February's tentative cessation of hostilities.
Fatah Halab is the main rebel alliance fighting around Sheikh Maqsoud and northern Aleppo, comprising a range of nominally Free Syrian Army groups, as well as Islamist factions such as Jabhat al-Shamiya and the Noureddin al-Zinki Brigades - some of whom have reportedly been on the receiving end of US training and weapons in the past.
In May, Amnesty International stated that rebel fighters had "repeatedly carried out indiscriminate attacks that ... struck civilian homes, streets, markets and mosques". The rights organisation also repeated earlier allegations that rebels may have used chlorine gas during an April 7 bombardment of Sheikh Maqsoud, although Jaysh al-Islam, the faction often blamed for the attack, has strenuously denied these claims.
On the Kurdish side, the report also documented "at least 23 civilians ... killed by YPG shelling and sniper attacks in opposition-held areas".
Aleppo is a city divided, in tatters, constantly subject to change - but Sheikh Maqsoud's prime strategic location, and the complex dynamics running through it, suggest that the rebel-Kurd conflict-within-a-conflict will not end soon.
Source: Al Jazeera