Aleppo's ancient Umayyad mosque, which slid back into rebel control for a third time after prolonged clashes, offers a chilling window into the intractability of the Syrian civil war, now in its third year.
The iconic mosque in Aleppo's labyrinthine Old City has been a key battleground since last July, with rebels seeking the ouster of Bashar al-Assad's regime laying siege twice but each time only managing to retain control for less than 48 hours.
Rebels overran the centuries-old mosque -- scarred by bullets and littered with charred relics and artefacts -- for the third time late February and have since managed to hold sway through weeks of erratic shelling and "guerrilla" sniper attacks.
But Free Syrian Army (FSA) rebels acknowledge that until the neighbouring regime-controlled Citadel -- a medieval fortified palace overlooking the mosque that offers Assad's men a strategic high ground -- is captured, their grip remains shaky.
The hilltop Citadel, a fine military vantage point to launch tactical shelling and sniper raids, has stubbornly remained elusive and the rebels are able only to maintain an uneasy stalemate with no visible sign of a way forward.
"Neither side (is) able to establish a monopoly of force across the entire country," said Elizabeth O'Bagy, a Syria expert at the Washington-based Institute for the Study of War (ISW).
"The battle lines in Syria continue to ebb and flow with both the rebels and the regime taking territory in some areas and losing territory in others," she told AFP.
Syria has paid a heavy price for the brutal impasse, with the war leaving more than 70,000 people dead, millions displaced and countless cities and neighbourhoods ravaged.
But at the mosque, rebel comrades wielding homemade grenades, guns and bandoleers of bullets remain defiant in the face of near-daily shelling since taking control of the site.
One group warming their hands by a smouldering bonfire stood up at routine intervals, especially after every new round of shelling, to bellow "Allahu akbar" (God is greatest!) in unison -- to signal to regime soldiers that they remain undefeated.
The fighters tread a delicate tightrope between holding control over the mosque, an archaeological treasure in the UNESCO-listed Old City, and not damaging it, FSA fighter Abu Omar said, fingering his prayer beads.
But it has suffered extensive damage anyway. The bullet-pocked and soot-stained walls bear the physical scars of a messy war.
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Antique furnishings and intricately sculpted colonnades have been charred, valuable Islamic relics ransacked, and ancient artefacts -- including a box purported to contain a strand of the Prophet Mohammed's hair -- looted.
The place was once filled with worshippers who prayed on green and gold velvet carpets. Rebels, sandbag bunkers and rolls of barbed wire now surround it like a garrison.
But the rebels have managed to salvage ancient handwritten Koranic manuscripts and have hidden them in a "safe place", lest the mosque slip out of their control again.
"They (regime soldiers) can watch everything from the Citadel," said Abu Omar, revealing a picture of himself on his cellphone posing with the retrieved scriptures. "We don't want it to fall back into the wrong hands."
The first two times the mosque slipped away, he said, a regime sniper planted on the minaret of the mosque caused much grief. They could not reach the minaret due to non-stop shelling, but were able to take him down in their third attempt.
And another gambit paid off. The rebels gave up access to two adjacent cobblestone streets leading up to the mosque to regime forces and then cornered them from behind. "That trick was a blessing from Allah," Abu Omar said.
Rebel snipers now patrol all the access points from which the regime forces may try to retake the site around the clock, he added.
But AFP's chilling video from last year shows how dramatically the army retook the mosque from the rebels, overwhelming them with explosives while shelling and bombing their way in.
And such raids in the future by troops launching invasions from the Citadel can't be ruled out. An Islamic landmark with Greek, Roman and Byzantine ruins, the Citadel has been an icon of Arab military might for centuries.
Its deep moat, connected to a number of underground passageways and caves, and other defence mechanisms continue to be as decisive now as they were hundreds of years ago.
Moreover, the regime army is equipped with superior heavy artillery, mortars, tanks, helicopters and night vision equipment.
"The rebels have shown an ability to target key centres of the regime, but have faced difficulties in holding territory. The regime has the ability to go on the offensive and retains military superiority," ISW's O'Bagy said.
"The only way that this type of stalemated fighting may shift is if there were to be significant support given to the opposition to shift the balance of power in their favour. Otherwise, there is going to be a long war of attrition ahead."