The battle for Aleppo is bound for a brutal end

They tell us this is Free Syria, but it is a fragile and vulnerable liberty.

Just how vulnerable becomes terrifyingly clear at night.

Shells whistle overhead and rockets explode all too close to comfort. Worst is the second or two of silence as we wait for the explosion, wondering where the bomb will fall.

Between the deafening blasts there’s the high-tempo repeat rhythm of heavy machine gun fire. The bombardment starts at midnight and continues until dawn is beginning to break.

We are sheltering on the fringes of Aleppo, and from here north to the border with Turkey, the countryside has been cleared of 'Assad’s army.'

So says a local rebel commander as he shows off the evidence of that mighty force in retreat. It is strewn along the main road in the burnt out, smashed up remains of the regime's Russian-made battle tanks.

By the gaping ruin of one armoured personnel carrier lies the tattered uniform of a Syrian Army soldier. There are bodies still inside some of the wrecks. But there are no survivors.

John Ray reports on the continuing fight for supremacy between government and rebel forces in Aleppo.

This is a brutal fight to the death. Neither side is taking prisoners.

The commander’s name is Ali and before the uprising he was a photographer. Now he wields an AK47, and boasts of sending his men into battle in Aleppo.

"First Aleppo, and then Damascus. We will take the Presidential Palace. Assad, we will kill you," he tells his men.

It's a rallying cry we hear time and again but in reality this is revolution reliant on bravery and bravado and often not much else. I see few signs of the heavy weapons and fresh ammunition the rebels need to defeat Assad's well-equipped, modern army.

Watching the skies over Aleppo, we see helicopter gunships targeting rebels on the ground armed with rifles.

Still, the Free Syrian Army soldiers who first entered the city nine days ago now claim to control a number of districts in the south and east of Aleppo. They number in the high hundreds – far fewer than the ranks of Syrian Army forces who have re-enforced the city.

The sound of shelling or gunfire is almost constant. This weekend has witnessed a sharp escalation in the fighting.

Both sides know the battle for Aleppo, the country's commercial hub, will help decide the fate of the whole country.

Syria's second city has escaped much of the violence in 16 months of turmoil. Now it is braced for some of the worst.

In a suburb of the city, we meet a detachment of Free Syrian Army soldiers. Some are no older than teenagers. They are nervous warriors.

They guide us, creeping through a warren of back-alleys and across a rubbish dump, so we can see what they are up against.

"Be careful of their snipers. They are everywhere," a young boy tells us.

A glimpse over a wall reveals Assad's tanks dug in, a fearsome line of steel.

The rebels' prized weapons amount to a couple of anti-aircraft machine guns and an armoured car - all seized from the army. But they are kept under canvas and camouflaged by branches from an olive tree. The rebels know that to commit them to battle would mean their certain destruction.

"We know he has tanks and helicopters, but we are fighting for a cause. We are fighting for our freedom. They are fighting for nothing," says their leader.

This was a district of 30,000 people. Now the streets are deserted and the houses empty. Almost everyone has fled, taking whatever they can with them.

A middle-aged man, his wife, daughter and elderly mother cram carpets into their car. The old woman pauses just long enough to point to a plume of thick black smoke rising over the houses and to curse Assad.

The fate of Aleppo seems destined to be settled in blood. Mohammed, an activist, tells me if he had his way it's not just the president, but every Alawite who would be hunted down and killed.

Another says: "The regime tortures and kills our woman and children. The worst we do to them is put a bullet in their heads.’’

It is a war that respects no convention and no rule. Nor is there room for innocents.

I think of Commander Ali’s daughter, a pretty girl of eight or nine, with fair hair and pale, sad eyes. She and her friends parade the rebel Free Syria flag up and down the stairwell of their home that has somehow survived the devastation of battle.

When they finish playing, she carefully folds up the flag and hides it away. No one can be sure Assad and his army won't be back with a thirst for revenge.