The House of Commons vote in favour of British air strikes against Isis being extended from Iraq to Syria could be interpreted as the symbolic moment when Britain began its fourth military intervention in the Middle East since 2003. Hilary Benn made his striking emotional appeal for Britain to confront Isis just as we once confronted fascism.

Impressive words, except that that is precisely what we are not going to do. We are seeing one of those episodes when the Government claims to be doing great things and its opponents give substance to this ploy by taking it more seriously than it deserves by opposing it root and branch. An additional eight British aircraft are not going to make much military difference in the US-led bombing campaign in Iraq and Syria which has been going on since August 2014. Given that only 17 per cent of the 59,000 coalition sorties have resulted in air strikes, there are already far more planes in the air than there are targets available.

RAF planes launch second round of strikes on Isis oil field in Syria

Political action by Britain is, in any case, constrained by the US, which does not want Isis, President Bashar al-Assad or the forces headed by the al-Qaeda affiliate, the al-Nusra Front, to win the Syrian civil war decisively. Washington is trying to pretend that there is a moderate Syrian constituency opposed to these three parties capable of taking power in Damascus. David Cameron similarly expresses belief that not only does such a moderate force exist, but that it numbers 70,000 fighters, many of them members of the Free Syrian Army, an institution that was always an umbrella group and largely disintegrated two years ago.

It is easy to be derisive about these convenient fantasies, but they are important because they mask a dangerous vacuum at the heart of American and British policy. Worse, they act as a replacement for realistic policies and doom Syria to an endless war; powerful players inside Syria cannot be ignored, if there is ever to be a ceasefire between government and non-IS factions. This unwillingness to recognise who really has military strength inside Syria may doom the talks in Vienna, which are aimed at bringing about an end to the war.

So far, US-led air strikes and Russian intervention have not altered the military balance and the war is still sucking in new participants. While Britain was agonising over its very limited intervention last week, a Turkish battalion with tanks suddenly turned up outside Mosul in northern Iraq. The Iraqi government said it had not invited them in and asked them to leave. They are in a camp used by Sunni Arabs and former police in the city, who belong to a private army raised by the former local governor, Atheel al-Nujaifi, who fled when Isis captured it. This means that one more army has entered the conflict.

There is a more important change on the battlefield further west, where Russia is setting up a new air base in preparation for a Syrian army attack on Isis at Palmyra. Russian planes, which have hitherto operated out of Hmeimim base on the Mediterranean coast, will now also use Shaayrat base in Homs province, where new runways are being built. “The Syrian regime forces are about 3km from Palmyra and are advancing from the south and west,” Rami Abdel Rahman, who heads the pro-opposition Syrian Observatory for Human Rights, has said. Syrian troops have already reached al-Qaryatayn, a largely Christian town captured by Isis in the summer. Russian planes launched 40 air strikes around the town in a 24-hour period. There are also reports of Russia sending heavy artillery to Syria.

This opens up an interesting prospect. Western governments and media have claimed, ever since they started on 30 September, that Russian air strikes were directed at supposed moderates who were fighting Assad. This was largely propaganda, but it was just plausible because the strikes were initially directed mostly against non-Isis forces in Latakia and Idlib, where the Syrian army had suffered defeat earlier in the year. But if the Russians and the Syrian army directly attack IS in central Syria, how will the US, Britain and France respond? It will be difficult denounce it as one more cynical manoeuvre by Moscow.

In reality, Russian military intervention hitherto has never been as substantial as Moscow has claimed and its critics have alleged. It has sent fewer than 100 fixed-wing aircraft and helicopters. With this Russian air support, the Syrian army made some ground, but has won no decisive victories around Aleppo and in places it has been driven back.

British jets prepare for air strikes in Syria Show all 10 1 /10 British jets prepare for air strikes in Syria British jets prepare for air strikes in Syria A Tornado jet takes off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria British jets prepare for air strikes in Syria Pilots and ground crew prepare combat aircraft Panavia Tornados at RAF Marham at RAF Marham, UK Getty British jets prepare for air strikes in Syria A Eurofighter Typhoon jet takes off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria British jets prepare for air strikes in Syria A RAF Tornado arrives at RAF Akrotiri to begin operations in Akrotiri British jets prepare for air strikes in Syria A Tornado jet ahead of taking off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria, the Ministry of Defence has confirmed. The air strikes were carried out within hours of a vote by MPs in the Commons to back extending operations against Isis from neighbouring Iraq British jets prepare for air strikes in Syria Personnel work on a British Tornado after it returned from a mission at RAF Akrotiri in southern Cyprus British jets prepare for air strikes in Syria Two RAF Tornado GR4's, both with remaining weapons ordnance, approach RAF Akrotiri in Cyprus, as they return to the base after carrying out some of the first British bombing runs over Syria British jets prepare for air strikes in Syria A RAF Tornado takes off from RAF Akrotiri, on the Mediterranean island nation of Cyprus British jets prepare for air strikes in Syria A Tornado jet leaving RAF Lossiemouth in Scotland British jets prepare for air strikes in Syria AKA RAF Tornado arrives at RAF Akrotiri to begin operations in Akrotiri, Cyprus. The RAF has sent two further Tornado aircraft and six Typhoons to bolster aircraft now flying sorties to both Iraq and Syria

The Russians have seen Isis retaliate by blowing up a Russian civilian plane and the Turks shooting down a Russian military jet. This is now a war that Russia cannot afford to lose, if it wants to keep its enhanced status as a great power. It may well be in Russian interests to deepen its involvement in Syria, using its air power in combination with the Syrian army, which is the largest regular force in the country.

Of course, Syrian politics is not that simple. An advance by one external player and its domestic proxy in Syria is matched by a counter-move by another player. Nothing in Syria happens in isolation from the regional struggle between Sunni and Shia and between the Gulf monarchies and Iran. One effect of the success of US-led negotiations with Iran on its nuclear programme was to lead Saudi Arabia to undertake a more aggressive policy against Iran and its allies earlier this year.

Saudi Arabia started air strikes in Yemen against the Houthis, whom it sees as Shia and pro-Iranian, and increased its support for anti-Assad rebels in Syria. It reportedly abandoned its previous policy of not supporting al-Qaeda-linked armed opposition and combined with Qatar and Turkey to break the stalemate in northern Syria. They created the Army of Conquest, most of whose fighters come from al-Nusra and Ahrar al-Sham, which inflicted several defeats on the outgunned and outnumbered Syrian army. Realising that it faced defeat, the Russians, Iranians and Hezbollah all increased their involvement, to turn the tide back in favour of Assad and his forces, which they have now done.

How will the Sunni states respond to this setback to their hopes of defeating Assad, after their successes in May? Much depends on what Turkey does now, as it sees its 550-mile southern border increasingly under the control of Kurds and possibly, in future, the Syrian army. The US is demanding that Turkey finally close the 60-mile stretch of border west of the Euphrates that is Isis’s last access and exit point to the outside world. The US estimates that the Turkish army needs to deploy 30,000 soldiers to do this.