As Aleppo goes, so goes Syria’s rebellion. The city is crucial to the mainstream opposition’s military viability as well as its morale, thus to halting the advance of the Islamic State (IS). After an alliance of armed rebel factions seized its eastern half in July 2012, Aleppo for a time symbolised the opposition’s optimism and momentum; in the following months, it exposed the rebels’ limits, as their progress slowed, and they struggled to win over the local population. Today, locked in a two-front war against the regime and IS, their position is more precarious than at any time since the fighting began. Urgent action is required to prevent the mainstream opposition’s defeat: either for Iran and Russia to press the regime for de-escalation, to showcase their willingness to confront IS instead of exploiting its presence to further strengthen Damascus; or, more realistically, for the U.S., Europe and regional allies to qualitatively and quantitatively improve support to local, non-jihadi rebel factions in Aleppo. Any eventual possibility of a negotiated resolution of the war depends on one course or the other being followed.

Rebel-held areas in and around Aleppo remain the most valuable of the mainstream opposition’s dwindling assets. Sensing weakness, the regime and its allies have invested significant resources in trying to retake the city; they now appear to be on the verge of severing the last rebel supply line linking it to Turkey. Still, the rebels maintain certain advantages. The armed factions in and around the city include some of the rebellion’s most powerful and popular. The location near the Turkish border facilitates the flow of supplies and communication. The regime’s task is thus more difficult than at Homs and Damascus, where brutal siege tactics compelled acceptance of truces on its terms. Yet, even a partial siege of the rebel-held parts of Aleppo could deal an enormous blow.

To its east, the mainstream opposition faces a second deadly foe: IS, formerly ISIL, the Islamic State of Iraq and the Levant, riding high after victories in western Iraq and eastern Syria. In January 2014, Aleppo was ground-zero for IS’s most humiliating setback, when rebels drove it from the city and its western and northern hinterlands, forcing it further east. But today, with much of the rebel force tied down on one front against the regime, IS is making headway north of the city, toward the heartland of northern Syria’s most prominent mainstream rebel factions.

A combination of regime and IS victories in and around Aleppo would be devastating not only to local rebels, but to the Syrian opposition as a whole. The loss of territory and morale would reverberate throughout the country, pushing many to give up the fight or join a more powerful militant force: IS.

The regime and IS are not bedfellows, though mutual restraint in the first five months of 2014 gave some that impression. Rather, and despite recent clashes, they share some short- and medium-term interests: chiefly the defeat of mainstream rebel groups backed by the opposition’s state sponsors, in particular those credible with local populations. For the regime, their defeat would eliminate what remains of the only existential threat it has feared: the prospect of robust Western military support to armed opponents. For IS, it would remove most of its meaningful competition, so it could eventually establish a monopoly on armed resistance to an unpopular Iranian-backed dictator, much as in Iraq.

At stake in Aleppo is not regime victory but opposition defeat. The war would continue should that occur, pitting regime and allied forces that lack the capacity to reconquer chunks of northern and eastern Syria or to subdue them through compromise against an emboldened IS that would gain strength by attracting rebel remnants. Between such antagonists, there would be no prospect of a political resolution and little hope of restoring the integrity of Syrian and Iraqi borders.

The situation is grim, but all is not yet lost. The bulk of the armed opposition is dominated by groups that, unlike IS, have demonstrated responsiveness to local populations and state sponsors. Their shortcomings are manifold and performance uneven, but the most successful of them have begun to show political pragmatism needed not only for continued viability but also to resolve the war.

It is past time for state supporters on both sides to acknowledge that the status quo leads to disaster. For Iran and Russia, this means recognising that – lip service to a negotiated solution and counter-terrorism notwithstanding – the regime strategy they facilitate renders resolution impossible and strengthens the jihadis it claims to combat. For the mainstream opposition’s principal backers – the U.S., Saudi Arabia, Qatar and Turkey – it means acknowledging that their tough words, meagre support and strategic incoherence have helped produce the current desperation. Recent modest increases in support for armed groups will not prevent their defeat, though they may shift the political and ideological balance among them. Syria is sliding toward unending war between an autocratic, sectarian regime and an even more autocratic, more sectarian jihadi group that, on present trends, will potentially destabilise the Middle East well beyond Syria and Iraq.

The fall of greater Aleppo to regime and IS forces would do much to bring this about. There are two means of avoiding it:

• Best would be through immediate negotiation and implementation of a local ceasefire between the regime and anti-IS rebel forces in Aleppo. This would allow the latter to dedicate their resources to halting and eventually reversing IS gains. It would require a dramatic shift in regime strategy: from prioritising defeat of the mainstream opposition to prioritising the fight against IS, and recognising that IS cannot be defeated without conceding a role to the mainstream opposition. If the regime and its allies are serious about weakening jihadis, they should immediately show willingness to halt their offensives in Aleppo and withdraw to positions from which their forces no longer threaten the main rebel supply line to the city. If such a ceasefire is offered, mainstream rebels in Aleppo should accept it and ensure that their anti-IS jihadi allies do the same. The mainstream opposition’s state backers should pressure them to do so.
   
• Such a regime shift appears unlikely. In its absence, the only realistic alternative is for the opposition’s state backers to improve support, qualitatively and quantitatively, to credible non-jihadi rebel groups with roots in Aleppo. That could become more costly to the regime and its allies than a local deal, as some of the support would inevitably be deployed against regime forces. The option would also carry costs for the opposition’s backers. To be effective, it would entail, at minimum, an increase in cash, ammunition and anti-tank weapons delivered to mainstream rebel factions – some of which could end up in jihadi hands; it would also require a higher level of investment by the U.S. and of cooperation among Saudi Arabia, Qatar and Turkey. Even if successful, this effort would not tilt the military balance in favour of the mainstream opposition – but it could prevent its defeat, halt IS gains on a key front and thus preserve the chance for an eventual political resolution.

Other prominent options at the centre of the Western policy debate would likely be counterproductive. Calls for partnership with the Assad regime against jihadis are ill-conceived. Until regime forces fundamentally revise their posture and abandon the habit of exploiting jihadi gains for their own benefit, they have little to offer in the fight against IS. Their current dependence on indiscriminate tactics and Iran-backed militias is fuel for jihadi flames. Proposals to expand U.S. airstrikes against IS into Syria are incomplete tactical prescriptions in search of a strategy. IS gains can only be halted and eventually reversed through the empowerment of credible Sunni alternatives, both locally and within the context of national governance. In the absence of a broader strategy to accomplish that, airstrikes against IS would accomplish little; indeed, the propaganda benefits that would accrue to the group could be more important than the tactical setbacks it would suffer.

There are, of course, risks in the two more promising policies outlined above. But the failure of any and all parties to take some risk will lead only to disaster.

Beirut/Brussels 9 September 2014