A couple of years ago, an Iraqi minister was speaking to a senior American general about the war in Syria and why President Bashar al-Assad was still in power when Muammar Gaddafi had been swiftly overthrown and killed by rebels in Libya in 2011. “The big difference between now and then is that Russia is back as a great power,” replied the general, recalling that, in Libya, Russia had assented to Nato military intervention to save Benghazi falling to Gaddafi’s tanks. Russian compliance opened the door to a determined and successful Nato campaign to give enough support to Libyan rebels to defeat the regime.

In Syria, by way of contrast, Russia has given the Assad government enough military and diplomatic support to avoid defeat. Russia is Syria’s main arms supplier and has prevented all-out Western intervention along the same lines as Libya. Vladimir Putin’s Russia is nowhere near as strong as the Soviet Union, but the US and Britain have also lost strength in the Middle East over the past decade because of the failure to achieve their ends in wars in Iraq and Afghanistan. Over the past year, the US has compounded this sense of weakness by failing to stem the advance of Isis despite a year of air strikes against its fighters.

It is important to take on board this failure of current policies to stop Isis before assessing what should now be done by the US, UK, Russia and their allies. Wishful thinking has so far predominated: President Barack Obama responded to news of the first Isis successes last year by comparing the extremist group to a junior basketball team playing out of its league. Soon afterwards Isis captured most of northern and western Iraq.

In May this year, at the very moment the US military was boasting that its air strikes had stopped Isis expanding, the jihadi militants captured Ramadi in Iraq and Palmyra in Syria. Their advance is still going, Isis fighters capturing the Christian town of al-Qaryatayn last month, bringing them within 22 miles of the crucial north-south highway, the loss of which would be a crippling blow to Assad. On Monday, Isis fighters captured the regime’s last major oilfield at Jazal.

In other words, there are two international crises stemming from the catastrophic civil war in Syria: one is the exodus of Syrian refugees arriving in Europe; the other is the expansion of this so-called Islamic State (Isis), which already controls half of Syria and will soon control more.

ORDER IT NOW

There was a flurry of diplomatic activity in August, but overall there is an astonishing lack of action by the main powers to bring the conflict to an end, though it becomes ever more essential to do so. The strongest parties within Syria are not going to negotiate a peace because the armed opposition is dominated by Isis, Jabhat al-Nusra and Ahrar al-Sham, al-Qaeda-type movements that plan to kill their enemies, not talk to them. For his part, Assad shows no real willingness to share power with anyone – though power shared institutionally or geographically is the only way this civil war can be ended.

There is something hypocritical about US criticism over the weekend of possible increased Russian military aid to Syria, though the Russians deny this is happening, because nobody would be more horrified than Washington if the Syrian army collapses and Isis and al-Qaeda become the dominant force in Syria. The US request to Greece to deny Russia permission for overflights by planes, likely to be carrying weapons to fight Isis, is a depressing sign that Obama has yet to come up with a sensible policy in Syria.

Western leaders have a curiously ambivalent attitude towards Russia in which it is, at one moment, a diplomatic mouse that can be safely ignored and, at another, a reborn Soviet Union whose imperial ambitions must be restrained. In handling the Syrian crisis, Russia is bound to be a leading player in stopping Isis because it supplies the weapons to do so and, similarly, in negotiating a peace because Assad must keep in step with Russia if he is to survive. Moscow does not have the strength to bid for a hegemonic role in Syria or the Middle East, so this is not a moment for knee-jerk Cold War reactions.

Without Russia joining with the US to press their allies inside and outside Syria towards a settlement, the war will go on and the only winner will be Isis and the al-Qaeda clones.