Russia could be poised to beome a super power again after agreeing with the US to launch what amounts to a joint air campaign against the two main extreme Islamist groups in Syria. If the ceasefire that starts at sunset on Monday holds for seven consecutive days and the UN is able to deliver aid to besieged people in Aleppo, then the US and Russia will establish “a joint implementation centre” that will organise joint military targeting by American and Russian aircraft directed against Isis and Jabhat al-Nusra, the Syrian branch of al-Qaeda which has relabelled itself – with al-Qaeda publicly assenting to a break with its affiliate – as Jabhat Fateh al-Sham.

For the US and Russia to plan and implement what may be a lengthy air campaign in Syria is perhaps the most striking aspect of the deal announced in Geneva early on Saturday morning. If the plan goes ahead, it goes a long way towards elevating Russia back to the status of a superpower – at least in the Middle East – that it lost with fall of the Soviet Union in 1991. Military partnership with the US, though in pursuit of the single objective of attacking Isis and al-Nusra, is a powerful incentive for Moscow to insist that the Syrian air force stop combat missions over all opposition areas, aside from those held by Isis.

The US and Russian aim is combat both “terrorist” movements, but it is difficult to see how the campaign will work. The plan is for moderate anti-Assad armed groups to decouple themselves from al-Nusra, which will then be targeted by air strikes. But, it is generally agreed that such moderate groups are thin on the ground in Syria and those that turn against their former allies in al-Nusra too abruptly may not live long enough to enjoy the protection of a US-Russian air umbrella. Nusra is not only well armed, organised and present in many parts of Syria, but it enjoys substantial political support from the Sunni Arab population. It will not be easy to weaken or eliminate.

Syria’s civil war: More than 100 killed in air raids.

There is a mysterious element in the US-Russian air campaign. Air strikes by both countries have been effective against Isis and al-Nusra, but they require ground troops to call in the air attacks against identifiable targets. For all their fanaticism, the extreme jihadis have not been able to withstand this type of bombardment and have suffered heavy casualties whenever they tried to do so, such as during the four-and-half month long siege of the Syrian Kurdish city of Kobani in 2014/15 and in Ramadi and Fallujah. But in the new phase of the air war in Syria it is not clear who is going to provide the ground troops to cooperate with the massive air power overhead and occupy territory from which Isis has been driven.

In pictures: Russian air strikes in Syria Show all 19 1 /19 In pictures: Russian air strikes in Syria In pictures: Russian air strikes in Syria Syrian boys cry following Russian air strikes on the rebel-held Fardous neighbourhood of the northern embattled Syrian city of Aleppo Getty In pictures: Russian air strikes in Syria Russian defense ministry spokesman Major General Igor Konashenkov speaks to the media in Moscow, Russia. Konashenkov strongly warned the United States against striking Syrian government forces and issued a thinly-veiled threat to use Russian air defense assets to protect them AP In pictures: Russian air strikes in Syria Syrians wait to receive treatment at a hospital following Russian air strikes on the rebel-held Fardous neighbourhood of the northern embattled Syrian city of Alepp Getty In pictures: Russian air strikes in Syria Russian Deputy Defense Minister Anatoly Antonov speaks at a briefing in the Defense Ministry in Moscow, Russia. Antonov said the Russian air strikes in Syria have killed about 35,000 militants, including about 2,700 residents of Russia AP In pictures: Russian air strikes in Syria Jameel Mustafa Habboush, receives oxygen from civil defence volunteers, known as the white helmets, as they rescue him from under the rubble of a building following Russian air strikes on the rebel-held Fardous neighbourhood of the northern embattled Syrian city of Aleppo Getty In pictures: Russian air strikes in Syria Civil defence members rest amidst rubble in a site hit by what activists said were airstrikes carried out by the Russian air force in the town of Douma, eastern Ghouta in Damascus, Syria Reuters In pictures: Russian air strikes in Syria A girl carrying a baby inspects damage in a site hit by what activists said were airstrikes carried out by the Russian air force in the town of Douma, eastern Ghouta in Damascus, Syria Reuters In pictures: Russian air strikes in Syria Civilians and civil defence members look for survivors at a site damaged after Russian air strikes on the Syrian rebel-held city of Idlib, Syria Reuters In pictures: Russian air strikes in Syria Civilians and civil defence members carry an injured woman on a stretcher at a site damaged after Russian air strikes on the Syrian rebel-held city of Idlib, Syria Reuters In pictures: Russian air strikes in Syria Volunteers from Syria Civil Defence, also known as the White Helmets, help civilians after Russia carried out its first airstrikes in Syria In pictures: Russian air strikes in Syria The aftermath of Russian airstrike in Talbiseh, Syria In pictures: Russian air strikes in Syria Smoke billows from buildings in Talbiseh, in Homs province, western Syria, after airstrikes by Russian warplanes AP In pictures: Russian air strikes in Syria Russian Air Forces carry out an air strike in the ISIS controlled Al-Raqqah Governorate. Russia's KAB-500s bombs completely destroy the Liwa al-Haqq command unit In pictures: Russian air strikes in Syria Caspian Flotilla of the Russian Navy firing Kalibr cruise missiles against remote Isis targets in Syria Â© TASS/ITAR-TASS Photo/Corbis In pictures: Russian air strikes in Syria Russia claimed it hit eight Isis targets, including a "terrorist HQ and co-ordination centre" that was completely destroyed In pictures: Russian air strikes in Syria A video grab taken from the footage made available on the Russian Defence Ministry's official website, purporting to show an airstrike in Syria In pictures: Russian air strikes in Syria A release from the Russian defence ministry purportedly showing targets in Syria being hit In pictures: Russian air strikes in Syria Russia launched air strikes in war-torn Syria, its first military engagement outside the former Soviet Union since the occupation of Afghanistan in 1979. Russian warplanes carried out strikes in three Syrian provinces along with regime aircraft as Putin seeks to steal US President Barack Obama's thunder by pushing a rival plan to defeat Isis militants in Syria In pictures: Russian air strikes in Syria Caspian Flotilla of the Russian Navy firing Kalibr cruise missiles against remote Isis targets in Syria, a thousand kilometres away. The targets include ammunition factories, ammunition and fuel depots, command centres, and training camps Â© TASS/ITAR-TASS Photo/Corbis

Isis has become weaker over the past year. It won its last big victories in capturing Palmyra in Syria and Ramadi in Iraq in May 2015, and has since lost them both. More recently, it was drive out of Fallujah, which it had held for two-and-a-half years, by the Iraqi army backed by US-led air strikes. Last month, it lost its access to the outside world when the Turkish army sealed off the last strip of the Syrian-Turkish border open to it. But, though Isis is badly battered, it has not yet been decisively defeated. It has thousands of experienced fighters and can impact on the political agenda of the world by its terrorist attacks abroad.

Isis, despite its territorial losses in Syria, still holds Raqqa and a large part of the Euphrates valley. But the heart of the movement has always been in Iraq. It was its capture of Mosul in the summer of 2014 that enabled it to declare a caliphate and become a demonic new player on the world stage. Kurdish and Iraqi army forces are now gearing up for an attempt to recapture Mosul, by far the biggest population centre still held by Isis. If the movement cannot hold the city, then it overall power and influence in Syria and Iraq will be much reduced.

To assess the current mood in Mosul and discover how Isis is responding to the threat of attack, The Independent interviewed by email a local observer in the city, whose pseudonym is Hammad Abu Jasim. Given that Isis had just executed a woman and her daughter for talking by mobile phone from a high building in Mosul to relatives in Erbil, his discretion about his identity is understandable. It is worth quoting Abu Jasim at some length to give the flavour of what may the last days of Isis in Mosul.

There are signs of Isis moving its personnel within Mosul and out of the city. Abu Jasim says, “I saw a long queue of big vehicles carrying away the furniture, equipment and facilities of Mosul University colleges to other parts of the city and outside it. Daesh [Isis] intends to empty the public institutions in Mosul. In addition, it has launched a campaign against internet cafés in the last two days, and closed them if the owners have relatives outside Mosul.”

These are signs of nervousness by Isis. It is closing many of its military and security bases, presumably suspecting that their function is well known and they will be targeted by US-led air strikes. But more significant are signs that the financial resources of Isis are much reduced. Abu Jasim reports that “until last week, the families of Isis militants killed in the fighting were still receiving lump sums and salaries, but last week none were given. The families were told that their numbers were increasing and the caliphate's resources decreasing, so they had to support it at this critical time.”