For the past few weeks, British news-papers have been informing their readers about two contrasting battles in the killing grounds of the Middle East. One is Mosul, in northern Iraq, where western reporters are accompanying an army of liberation as it frees a joyful population from terrorist control. The other concerns Aleppo, just a few hundred miles to the west. This, apparently, is the exact opposite. Here, a murderous dictator, hellbent on destruction, is waging war on his own people.

Both these narratives contain strong elements of truth. There is no question that President Assad and his Russian allies have committed war crimes, and we can all agree that Mosul will be far better off without Isis. Nevertheless, the situations in Mosul and Aleppo are fundamentally identical. In both cases, forces loyal to an internationally recognised government are attacking well-populated cities, with the aid of foreign air power. These cities are under the control of armed groups or terrorists, who are holding a proportion of their population hostage.

Peter Oborne discusses the situations in Mosul and Aleppo with Seth J Frantzman

In Mosul, fewer than 10,000 Isis fighters control about a million people. In eastern Aleppo, it is estimated that about 5,000 armed men, the majority linked to al--Qaeda, dominate a population of about 200,000. In each case the armed groups use the zones they occupy to attack government areas with rockets, mortars and other weapons.

So Prime Minister al-Abadi in Iraq and President Assad in Syria face the same dilemma. Should they do nothing for fear of killing civilians? Or do they take air action and eliminate the so-called rebels, but at terrible cost in innocent blood as they wage merciless war against ruthless insurgents?

In both cases, enormous bloodshed could be prevented if the terrorist groups let the civilian population leave. Last month the UN special envoy to Syria, Staffan de Mistura, pleaded with Jabhat Fateh al-Sham (formerly al-Qaeda, but now decoupled and rebranded) to do just that: ‘One thousand of you are deciding the destiny of 270,000 civilians.’ He pointedly used the word ‘hostage’ to describe the way these civilians were being held by the rebels and not by Assad.

This episode highlighted the double standard about western reporting of these terrible problems. In Mosul, western reporters travelling with the invading Iraqi army publish pictures of joyful populations liberated from the jihadists. In Aleppo, the attempt to free the city from al-Qaeda control is portrayed as a remorseless attack on the civilian population.

Assad and his allies have carried out war crimes. But that is not the whole story. When I visited the government-held areas of Aleppo earlier this year, I met scores of people who had fled for their lives from al--Qaeda or Isis in the east of the city. They told me hideous stories of how these jihadists, very few of whom were Syrian, had enforced a brutal form of sharia law, abolished education in schools and forced women to wear burkas and stay at home.

In western Aleppo, I found a woman in a government building where she had come to collect her salary as a teacher (government employees in rebel-held areas are still paid by the regime, even though they are no longer allowed to work). She told me how she was preparing to return home to rejoin her husband and children. She had no doubt at all what fate awaited her: ‘The fighters are preparing ambushes with explosives. They are moving their wives and families out. They are keeping us as human shields.’

Western reports about the fighting in Mosul have made much of the liberated churches. Yet exactly the same narrative applies across Syria. Two years ago I joined Syrian government forces as they freed the eastern city of Maaloula (where Aramaic, the language of Christ, is still spoken). The famous monastery above the town had been dreadfully desecrated by al-Qaeda. In Aleppo, the Christian community has collapsed from 200,000 before the war to maybe 25,000 today. This is because Christians in Aleppo know that if the British and US-backed jihadists in the east win the war, they will be slaughtered.

A further double standard concerns the reporting of Russian and Syrian atrocities. Much has — rightly — been made of the so-called barrel bombs dropped on Aleppo by the Russians. Yet rebel commanders in eastern Aleppo use equally hideous weapons. Last April, fighters from Jaish al-Islam, backed by Saudi Arabia and considered moderate enough that American diplomats retain relations with them, admitted to using chemical weapons against the Kurds in Aleppo. This attack received almost no attention from the media, and failed to generate the faintest outrage in Britain.

Jaish al-Islam employ a so-called ‘hell cannon’ to fire gas canisters and shrapnel weighing up to 40 kilograms into civilian areas. These are every bit as murderous as the barrel bombs. Reports in the western press have suggested that hell cannons are examples of the engineering ingenuity of plucky rebels. Few journalists have dwelled on the fact that these improvised weapons have been deliberately used to kill hundreds of Aleppo civilians.

Yet another double standard applies to the destruction of hospitals. When I was in Aleppo, I interviewed Mohamad El-Hazouri, head of the department of health, at the Razi hospital. He told me that when rebel groups entered the city they put six of the 16 hospitals out of service, as well as 100 of the 201 health centres, and wiped out the ambulance service.

An Aleppo eye hospital, which had been one of the greatest treatment centres in northern Syria, had been turned into a jail for detainees by the rebels. He said that his workers went to great lengths to supply hospitals in the rebel areas. Often they were rebuffed.

There is a wider pattern at work here. When opponents of the West try to reclaim urban areas from terrorists, they are denounced. When our allies do the same — think of Israel in Gaza or the Saudis in Yemen — we defend them. We judge Assad by one set of rules, and ourselves and our own allies by another.