Isis blew up one of the last remaining bridges across the Euphrates at Ramadi this week as 300 of its fighters tried to hold on to the centre of the city, which has come under attack from Iraqi government forces supported by US air strikes. Here Isis is on the retreat, but in Syria it has recaptured the village of Mahein, south-east of Homs, from the Syrian army, which had seized it a few days earlier and had been expected to use the village to launch an attack to retake the city of Palmyra.

The recapture of a world famous city such as Palmyra, where Isis has publicly executed Syrian soldiers and blown up the ancient temples, would have been an important victory for President Bashar al-Assad. Failure to do so is a further sign that the Syrian army’s multiple offensives against Isis and the Syrian armed opposition, which is backed by Russian air power, have so far failed to win any big successes that would tip the likely outcome of the war in Assad’s favour.

It is a vast battlefield stretching 500 miles across Iraq and Syria from the outskirts of Baghdad to the mountains overlooking the Mediterranean. Every day there are skirmishes, bombings and battles, of which some are well publicised, but others are fought out in the semi-desert of eastern Syria and get scarcely a mention in the local or international media.

Probably, one of the most important military setbacks for Isis in recent weeks was the loss of al-Houl, a town captured by the Syrian Kurdish People’s Protection Units (YPG) on 13 November. This attack threatens the road linking Isis’s Syrian capital at Raqqa to Mosul and Isis’s oilfields in eastern Syria.

On the same day, Kurdish forces in northern Iraq recaptured the small city of Sinjar which had been taken by Isis the previous year when it slaughtered or enslaved the Yazidi inhabitants. Unlike al-Houl, this success was broadcast around the world and there was speculation about whether or not the self-declared Islamic State was beginning to crumble. But it soon became clear that Isis had decided not to fight to the finish in Sinjar and had pulled out after two days’ fighting against greatly superior numbers.

Western commentators hopefully predicted that the loss of Sinjar would cut Isis’s supply lines between Raqqa and Mosul, and so it did for a week or more. The price of vegetables doubled in the markets of Mosul, but soon fell when Isis hastily opened up a new route south of Sinjar and the trucks carrying vegetables started moving again.

The war in Iraq and Syria over the past four years is full of military engagements that were claimed as decisive at the time by one side or the other. Most turned out to be no such thing. In the summer of 2014, the Syrian army was forecast to be close to sealing off the rebel-held parts of Aleppo, but it failed to do so. In May this year the Syrian armed opposition, including Isis, Jabhat al-Nusra and Ahrar al-Sham, won some important victories in Idlib province in the north and Palmyra in the east. This provoked Russian air intervention and greater involvement by Iran and Hezbollah of Lebanon, which collectively has had the effect of stabilising the Assad government. But the battle-lines have not moved that much and the biggest impact of the Russian action is to make it clear that Assad is not going to lose the war, if this was ever on the cards. Russia cannot afford to see an ally, for whom it has done so much, be defeated without serious damage to its international standing.

This does not mean that Assad is going to win. No doubt support from Russian fixed-wing aircraft, helicopters and missiles has helped the morale and military capacity of the Syrian army. But it has not transformed the battlefield because al-Nusra and the others were always going to fight hard and the Syrian army remains short of combat troops. If the opposition advance has been stemmed or in places reversed, the Syrian army has yet to regain Idlib city, Jisr al-Shughur or Palmyra. It is a long way from winning a decisive victory, such as the capture of the eastern opposition-held half of Aleppo.

The same is true, in Iraq, even if the Iraqi army and Shia militias succeed in regaining Ramadi. Isis is averse to defending easily identifiable fixed positions where it is an easy target for the US-led air campaign. It recalls that it lost 2,200 fighters failing to capture the Syrian Kurdish city of Kobani in a four-and-a-half-month siege that ended in January.Isis would probably defend Mosul, Fallujah and Raqqa to the last, but it might give up other places as not worth the heavy casualties it would suffer trying to cling on to them. Its best strategy is to use its strength as a mobile guerrilla force, seeking out its enemies’ weak points and launching multiple attacks that catch the other side by surprise.

Contradicting this military approach is a political imperative that makes Isis different from al-Qaeda and other extreme jihadi movements. The difference is that it is a genuine state with an administration, taxation, conscription and total control over the civilian population. This means that it will have to fight for some of its territory and this is where it is vulnerable to the massive air power – in the shape of the US and Russian air forces – arrayed against it. It has become conventional wisdom to say that air power alone does not win war, but continual pounding by hostile aircraft does limit the kind of operations that Isis can conduct successfully and it shatters the infrastructure of roads, bridges, water and electricity supply used by soldiers and civilians alike.

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’s cocktail of tactics such as mass use of suicide bombers in vehicles packed with explosives were highly effective last year and in the first half of this year. Some 30 such bombs were used in May to breach the defences of Ramadi, including 10 armoured dump trucks that overwhelmed the defenders. But anti-Isis fighters are now armed with an array of anti-tank weapons that stop most of these vehicles before they can do any damage. Isis cannot shock and terrify its enemies in the way it did at the time of the fall of Mosul.