During this period, the only way to Aleppo was by plane because the army held a tiny peninsula of territory going to the airport – I flew out one night on a military aircraft crowded with wounded Syrian troops.

But the tables have turned. It is the rebels themselves who are now surrounded, along with the tens of thousands of civilians in their sector of the city – but they have no airport to sustain them.On the basis of so many other battles in this appalling war, there is unlikely to be any offensive for the centre of this greatest of Syrian cities; rather it will be a slow and grinding siege to force the insurgents to surrender.

In an ironic twisting of recent history, the two Shia villages of Nubl and Zahra – whose people had been surrounded by rebels and starved for three years, fed only by Syrian military airdrops – have now been retaken by the Syrian military.

The Shia, co-religionists of the Alawite people from which President Bashar al-Assad comes, have been cornered in several villages in the region, although their plight has gone largely unreported.

Now the people in the rebel-held part of Aleppo are going to feel the same sense of isolation – and, no doubt, the shellfire of their besiegers. There has always been a movement of people between the two sectors of the city – will these passages now be closed? And what of the tens of thousands of civilians streaming north towards Turkey?

Aleppo itself was late to join the war. By some kind of historical miracle, it remained disentangled from the conflict until 2012 when rebels – thinking they were en route to Damascus – managed to infiltrate into the ancient city. Its streets were then burned out in months of fighting. Now it appears to be the first of Syria’s large cities to be effectively back in the hands of the regime. What comes next? The retaking of the Roman city of Palmyra? The clearing of the lands around Deraa (of Lawrence of Arabia fame)?

And, much more dramatically, how soon will the Syrian army, its Hezbollah allies and the Russian air force set their course for the Isis “capital” of Raqqa?

Isis, which holds Palmyra, must be learning of the extraordinary developments of the past few hours with deep concern. The everlasting Sunni “Islamic Caliphate” in Syria doesn’t look so everlasting any more. Is this why the Sunni Saudis have suddenly offered to send ground troops to Syria? And why the Turks are so flustered? I doubt if anyone is weeping in Shia Iran.

Anyway, the Saudi military is already having its feet chewed off in the disgraceful Yemen war. As for the Turks sending their own Nato soldiers across the Syrian border – presumably at risk of being attacked by the Russians – that is a nightmare which both Washington and Moscow must avoid. Otherwise, we’ll find ourselves in another Gavrilo Princip moment – and we all know what happened in 1914.