The remains of the Isis fighters still lie on the desert floor outside the sand ramparts of the Kuweires air base in northern Syria. A skull, sockets staring at the sun; bones protruding from a military boot; and rotted torsos beneath a grey tarpaulin lie beside the colossal, burnt-out suicide tank they tried to drive through the earthen wall.

For three years, Syrian government soldiers and air force cadets and cooks and military teachers fought them off. By the count of air force Brigadier General Munzer Zaman, Syrian group commander of Kuweires, around 1,100 men defended their base. Eight hundred of them died.

Twice Isis managed to break through the perimeter of the 15-sq-km air base on the main highway to Raqqa, driving captured Syrian armoured vehicles packed with explosives and smashing them into hangars and an administration block. An intelligence officer called Maher leads us to a 30-metre high pile of concrete.

“Five of my friends died here,” he says. “We found a hand, part of a body, that’s all,” and he held his arms apart to show how little was left of them. The rest still lay beneath the rubble. “One of them was a general,” he says.

If the Syrian army survives this terrible war, the story of the siege of Kuweires, north of the great salt lakes in the desert 38 miles east of Syria’s largest city of Aleppo, will be told and retold as an epic of endurance and bravery. If it is defeated, the battles here will be denigrated as the brutal stand of a regime’s forces against the "martyrs" of Islam, the smashed villages and mosques surrounding the air base testimony to the cruelty of war. The crumpled villages are there all right, shell-holed, roofless, a cupola roof of a mosque lying on its own broken walls, a cemetery of powdered gravestones.

Syrian Air Force Group Commander Munzer Zamam Commander in his office at Koyeress airbase (Nelofer Pazira)

But after General "Tiger" Suheil and Major Saleh blasted their way down the highway to the relief of Kuweires six months ago, the battle did not end. All day while I am here, the batteries of 122mm guns are still banging their shells across the desert. Brig Zaman constantly breaks off his conversation to receive battlefront requests for artillery support from shouting soldiers, and he scrawls over his computer maps to check their coordinates and give permission to fire. The windows of his office rattle constantly with the blasts.

Even today, the lonely road to Kuweires runs up the eastbound side of the dual carriageway between burnt fields, scorched factories and blasted homes. "Liberating" besieged soldiers is a destructive business. You might find the villages of Fah and Meer el-Hossen on a map. But they are dead. Brig Zaman insists that Syria will be rebuilt “more beautiful than it was before the terrorists came” and one can only hope he is right.

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"Terrorists" means Isis and the al-Nusrah Front – Zaman makes no difference between them – and he has a bleak, harsh memory of the battles to defend his air base. “Our enemy,” he says, “had two choices: death and death. There was no other.” When I ask if he knew the Syrian pilot, Major Nowras Hassan, who had just bailed out over Nusrah territory on the Syrian-Lebanese border far to the west and been promptly executed by his captors, Brig Zaman nods. “Of course I knew him well. He was a married man, no children. But the ways of terrorists will not terrorise us. Our base was under siege for three and a half years. It was the largest siege in history after Stalingrad.”

Captured homemade Isis mortar on the Syrian airbase at Koyeress (Nelofer Pazira)

The casualties and the geography may be a miniature version of the German Sixth Army’s siege of the Soviet city, although there were some clear historical parallels. The "liberation" of Kuweires earlier this year could not have been achieved without Russian air support; and the graveyard of smashed Mig fighter-bombers, shell holes, dismembered trees and gun-pits have a distinctly Second World War flavour. So do the casualties. Nine air force students died when a suicide truck was crashed into the hangar in which they were sleeping. The Syrians buried their dead in cemeteries around the runways, 79 of them in separate graves beside the air-base swimming pool.

“Our mufti said prayers over them under the shellfire but there were no shots fired over their graves,” a major says. “When we were liberated, the bodies were dug up one at a time and placed in new coffins and inside was a glass jar with their names and details.” A wooden board with "grave No. 7" on it is marked: “Ahmed Ali Zohoud from Lattakia, died 7 July 2015.” Almost exactly a year ago. A mile away, rows of captured homemade mortars constructed by Isis mechanics lie in the grass near to an American-made construction vehicle attached to a massive iron drill that had ben used to build tunnels beneath the base.

“They tried to call up the officers on the base,” Brig Zaman says. “They sent papers over the walls with numbers of mobile phones our men could ring to defect. They offered safety corridors from the base if they wanted to desert. But our men were loyal. I even received a message with telephone numbers to ring in Saudi Arabia and Turkey. I gave the numbers to our intelligence people. These countries work for the Americans and for Israel. The only slogan we sent back was that we will win or face the consequences of being martyrs.”

Missile with origin defaced, fired at Syrian troops at Koyeress airbase 40 km east of Aleppo (Nelofer Pazira)

For two years, helicopters could still land under fire in the base, but then flights became too dangerous. They then relied on air drops for essential supplies. General Hasham Mohamed Younis, a teacher at the air academy at Kuweires, was in charge of air drops throughout the siege. “Our helicopters flew over at an altitude of 4km,” he says. “Our problems were wind, the weight of the 75kg and 120kg packages – because the parachutes used in the drops were made for the weight of men – and the terrorists shooting at the drops when they were parachuted down to us. Some drifted down over the enemy, but not many. We successfully received most of the diesel and kerosene and food and letters for cadets from their families.”

War stories there were aplenty. Gen Younis recalls how one package of food from a cadet’s family was packed beneath a parachute which was blown down into the Isis lines. After a few hours, a message was thrown over the wall addressed to the cadet. “The enemy said they had enjoyed his mother’s food,” Younis recounts. “They asked him to tell his mother to send more for them.”

One fuel-carrying helicopter was shot down en route to Kuweires, all but one of its crew burnt to death. The other, Pilot Ali Hosman, jumped out of the machine holding on to one of the parachutes and landed on a 14-year old boy on the ground. The boy lived. Hosman died five minutes later.

Driving across the runways and perimeter ramparts of this huge air base – the first Western journalist ever to visit Kuweires – it isn't difficult to see what a prestigious target it made for Isis. Battered Mig jets – one with its tail broken off – stand beside more captured ordnance, two unexploded missiles clearly bear Latin letters and numbers of Western origin, another bears the inscription of an Arab government depot with its country of origin carefully scratched out. The tanks and BMP armour Isis used appear to have been captured from the Syrians at the start of the war – they include a T-72 tank which has its own Isis numbering ("311" is stencilled below the rear chassis) and it is remarkable that any serviceable aircraft still survive. But I drive past untouched Hind helicopters and several new Migs.

The soldiers at Kuweires are in some ways lucky. At least one other air base was overrun by Isis and its defenders captured - they were then beheaded on film. No wonder Brig Zaman is harsh in his commentary of war. “We had no messages for our enemies – we replied with our weapons. These people who have this ideology, you can’t change them – but you can kill them.” And he makes a reference to Hama in 1982, where Syrian forces killed thousands following a Muslim Brotherhood uprising. His lesson is a grim if rather startling one. “In Syria, we are defending all the world’s humanity. If Syria is defeated, even Britain will not escape, nor France, nor Turkey, nor Jordan. They will be darkened with the same blood.”