ON DECEMBER 2nd the House of Commons voted by an emphatic majority to let British planes bomb Islamic State (IS) in Syria as well as Iraq. It was a symbolic step, aimed at showing solidarity with allies against barbarism. Although British Tornado fighters boast highly accurate Brimstone missiles and a sophisticated intelligence-gathering pod, no one imagines that air power alone can defeat IS.

The problem remains what it has been in Syria since air strikes against IS first began in September last year: the absence of competent, politically acceptable forces on the ground to work with, other than the Kurdish YPG (People’s Protection Units), who seldom venture outside what they see as Kurdish territory. David Cameron was derided for claiming that there are “about 70,000 Syrian opposition fighters …who do not belong to extremist groups” and who might be potential allies of the coalition against IS. The Kurds are not included in that count.

In fact, most experts agree with the prime minister’s intelligence-derived assessment. Charles Lister of Brookings Doha Centre reckons that there are over 100 armed factions with a total of 75,000 fighters, many of whom operate under the Free Syrian Army umbrella, who could be considered “moderate” by Syrian standards. Many of these have already been “vetted” by the CIA and are receiving weapons and other assistance, albeit on a fairly small scale. They do not yet remotely resemble a cohesive force. But with time and the right political incentives they could perhaps be formed into one.

The YPG militia, which numbers around 55,000, has shown its mettle by pushing IS out of Kobane and moving west to take on IS at Jarabulus, the last border town with Turkey it holds. But despite the YPG’s success when helped by coalition air power, its main interest is in carving out a contiguous area of control along the border with Turkey. Despite talk of it joining up with Sunni tribes and driving south to the IS stronghold of Raqqa, it has little appetite for doing so. Even if it did, the political consequences of helping Kurds to seize an Arab town would hardly be positive.

Even more problematic from a Western point of view is the idea of partnering with either Ahrar al-Sham or Jaish al-Islam, two big Salafist groups that have connections with Jabhat al-Nusra (JAN), al-Qaeda’s increasingly powerful Syrian affiliate, but who are opposed to IS and who can field between them up to another 30,000 fighters. Opinion is divided as to whether Ahrar al-Sham and Jaish al-Islam should be considered jihadists who are beyond the pale or potential allies against IS. Both are supported by Saudi Arabia and Qatar and will be at a conference bringing together all the elements of the “legitimate” (ie not JAN or IS) Syrian opposition to be held under Saudi auspices in Riyadh, probably next week. Ahrar itself appears to be split between pragmatists, who want to reassure potential Western allies by distancing themselves from JAN, and those still clinging to its jihadist roots. The label “moderate” that used to be attached to groups the West could support is being quietly replaced by a more flexible term, “mainstream”, which broadly means genuinely Syrian factions that have no interest in exporting jihadism. It is an important and necessary shift, says Jennifer Cafarella, who covers Syria for the Institute for the Study of War in Washington, DC. The Russian military intervention two months ago “massively complicates” an already confused situation, according to Emile Hokayem, a Syria analyst at the International Institute for Strategic Studies. By concentrating their air strikes on some of the groups the West sees as potential allies, the Russians are not only shoring up the regime of Bashar al-Assad, Syria’s brutal president, but they are also indirectly assisting IS, since IS is also fighting some of these groups. A peace process involving all the states that are party to the conflict will continue into a third round in Vienna next month. But it is hard to see how the differences between Russia and Iran on one side and the American-led coalition on the other can be resolved. Barack Obama’s attempts at this week’s Paris climate conference to convince Russia’s Vladimir Putin to make destroying IS the priority rather than saving his client, Mr Assad, fell on deaf ears.

An interactive guide to the Middle East's tangled conflicts Jordan has been given the unenviable task of deciding which parts of the Syrian opposition should be defined as terrorists and thus excluded from the peace process, but it is clear that Russia puts virtually all rebel groups other than the Free Syrian Army and the Kurds into that category. Mr Hokayem thinks it is ironic that nobody is suggesting putting the regime’s forces on the terrorist blacklist, given its continued use of barrel bombs against civilians. For the West, over-investing in this process risks alienating Syrian Sunni opinion even further, especially when Mr Assad’s survival, at least for a period, remains on the table in Vienna. Ms Cafarella warns that Russia is fuelling Mr Assad’s narrative of a struggle against terrorists and is manipulating the Vienna talks to that end.

Fight the tyrant and the terrorists

The disconnect with the political reality on the ground is stark. However much most of the opposition militias loathe IS, their priority is still to complete the revolution and topple the hated regime. Mr Hokayem says: “If you want to mobilise forces against IS, you have to deal with Assad on a parallel track. They see themselves as liberators, not mercenaries.”