Much was made in this week’s Commons debate on Syria of the need for a no-fly zone over Aleppo. Given that the Syrian government and the Russians have a monopoly of air power over the city, the idea of denting or deterring it might seem attractive. Hillary Clinton also advocated such a zone in Sunday’s presidential TV debate.

In 1991 the US and Britain imposed a successful no-fly zone over northern Iraq to protect the Kurds. But they were already at war with Saddam Hussein, having just defeated him in Kuwait. Saddam was on his own internationally, despised and isolated. He had no support from Russia or any Arab allies. The last thing he wanted was to confront the US any further. Enforcing a no-fly zone (even though it had no clear UN security council authorisation) involved no risk to the US or UK. Saddam made little effort to resist and not one of their manned aircraft was shot down.

Today’s situation in Syria is different. The Syrian air force is fully engaged and will not back down in its campaign to defeat its enemies in Aleppo. After three years of military stalemate, Bashar al-Assad feels he has regained the upper hand and is determined to retake his country’s largest city.

More importantly, the Russians are also active in the air. Imposing a no-fly zone unilaterally (it would never gain a security council mandate) would be a declaration of war on Russia as well as on Assad. The dangers are obvious. It is not just a question of a clash between western and Russian planes by accident. That might be the only risk if it was assumed the Russians would meekly leave the skies free. Why would they? They are not going to be deterred from a bombing campaign that appears to be helping Assad’s ground forces advance. For the west to confront them risks an incalculably serious war.

Many on the jihadi side would like nothing more than to see the two Satans – the west and Russia – destroying each other in a hot war. But for Britain and the US it is madness. Hillary Clinton seemed to recognise that in a speech to corporate donors, according to the latest Wikileaks release. “All of a sudden this intervention that people talk about so glibly becomes an American and Nato involvement where you take [out] a lot of civilians”, she said.

The second option is for Syrian government forces to retake the whole city

There are only three sensible ways to save Aleppo’s people. One is the voluntary departure of the jihadis who, in the words of UN envoy Staffan de Mistura, are holding civilians hostage. One could go further and say they are keeping eastern Aleppo’s civilians as human shields. Why, for example, have most people not left already, given the intensity of Russian bombing: is it that the jihadis are blocking people’s escape? Syria is also mired in a propaganda war, and in the heart-rending images that the rebels put out on social media about life and death in Aleppo, the seamier side of the armed groups’ control is suppressed.

Hundreds of civilians recently left the besieged Damascus suburb of Daraya after the rebels gave in, with no reprisals from Assad forces. Gunmen were even allowed to keep their weapons and were taken by buses to rebel-held areas in the north.

The second option is for Syrian government forces to retake the whole city, just as Iraqi forces retook jihadi-held Ramadi and Falluja in recent months. Iraqi barrel bombs and US airstrikes had left three-quarters of those cities in ruins, but civilians got the chance to rebuild their lives.

The concept of an Assad victory will stick in the throats of hundreds of thousands of Syrians who have lost so much in the fight against him. But if the secular multicultural tolerance of pre-war Syria is to be restored, it is better to deny victory to the Sunni extremists who pose the main opposition to Assad, whether it is Islamic State, the al-Qaida-linked Jabhat al-Nusra or similar groups.

The third option is a ceasefire. Last month’s Russian-US agreement provided for the superpowers to separate the al-Nusra fighters from those Syrian Islamists prepared to negotiate with Assad’s representatives in Geneva for a coalition government.

The ceasefire never took hold because the Islamists refused to split. Al-Nusra understandably did not want to be isolated and left vulnerable to a joint US-Russian air campaign. So they used their dominance among the Aleppo fighters to press the other groups to stick with them. For their part, the non-Nusra fighters feared an alliance between the Americans, the Russians and Assad’s army.

Having failed once, for the Russians and Americans to broker a new ceasefire is a tall order. The other options are equally difficult. But at least they tend towards de-escalation. Proposing a no-fly zone not only risks greater catastrophe for the people of Aleppo. It threatens to engulf us all.