Troops broke through Isis lines to the eastern city on the banks of the Euphrates some 1,400 days after it was surrounded by Western-supported Free Syrian Army (FSA) insurgents in the autumn of 2013.

Following hours of fierce fighting over the last 1.5 miles separating the two forces, the relief column met up with the city’s defenders at an army base on the western edge of the city.

The breaking of the siege sounded the death knell of the Isis death cult, now reduced to a handful of strongholds across eastern Syria and northern Iraq.

And with Western-backed factions observing a truce in most of the densely populated west of the country since early July — and UN-brokered peace talks ongoing in Geneva — the six-year war appears  to have entered its final stage.

The breakthrough also opened a lifeline to the estimated 125,000 of the city’s 200,000 residents still trapped there, who have depended on airdrops for supplies since Isis cut off the city’s airport last year.

That followed a prolonged air attack by the US-led Inherent Resolve coalition on Syrian government positions on Mount Thardeh, overlooking the airfield, which Isis immediately followed up with a large and well-co-ordinated assault.

After years of fighting in and around the city, the FSA captured most of Deir Ezzor in October 2013, two months afte an army column of 600 troops returned to the city to bolster its defences.
In April 2014 Isis drove the FSA out of the province and continued the siege.

With Raqqa — the de-facto Isis “capital” in Syria — under the control of the Kurdish-dominated Syrian Democratic Forces, the extremists had redoubled their assaults on Deir Ezzor in recent months in a last-ditch attempt to take the city.

But the defenders held firm and even pushed the besiegers back, inflicting heavy casualties with the help of scores of air attacks daily by the Syrian and Russian air forces.