It takes reckless courage to make predictions about Syria. But compared to a year ago, when the survival of the Assad regime looked increasingly problematic, the factors shaping the military and diplomatic outlook in 2016 are somewhat clearer.

The Assad regime looks set to remain in place. Unless there is a change in Russian and Iranian conclusions about their strategic interests in the survival of that regime, or a sudden reversal of military fortunes, or some internal falling out as pressures on the regime ease, Damascus will probably hold on to the territory it controlled at the start of the year. It may even add to that territory, depending on the degree to which Russian air power continues to be concentrated on rebel forces in western Syria. The fact that the al Qaida-linked Jabhat al-Nusra is embedded in almost all rebel groups in northern Syria provides the pretext (if any were needed) for the Russians to continue targeting all combat-capable opposition forces.

 The rebel groups remain chronically under-resourced, especially in terms of ammunition. They have lost momentum. Some minor elements will probably lose the will and capability to fight over the course of 2016. Others, lacking Western assistance, will integrate more closely with Ahrar al-Sham and Jabhat al-Nusra. They all face the prospect of increasingly effective use of Iranian and Russian forces, including Russian Special Forces, Iranian-backed militias, surveillance drones and the more adept use of artillery. Their leadership elements are being targeted more effectively by the Russians as well.

The war could be further escalated by the closer involvement of Saudi Arabia, which may be considering sending in ground forces via Turkey or from Jordan.

Without strong US backing, including close air support, a Saudi ground offensive in Syria directed against the Kurds or the Assad regime, rather than against ISIS in Raqqa, would risk outright military defeat. The personalities and perceptual predispositions of their leaderships clearly favour fighting on, but Turkey and Saudi Arabia have also to consider the uncertain political consequences of trying to prosecute a war, without clear and realistic political objectives or a viable exit strategy, that could well humiliate their governments.

For the US, the central strategic concern remains removing the threat posed by ISIS in Iraq and Syria, rather than seeking directly to determine the fate of the Assad regime. The strategic task, however, is considerably more complex than its military dimension. Whereas Russia would probably countenance a continuation of the insurgency against the Assad regime (part 2 of this series explains why), the US wants to craft a diplomatic process offering the prospect of a regionally-endorsed political resolution of the Syrian conflict.

Whereas global attention is focused on developments in Aleppo and the north-west of Syria, during 2016 the question of Raqqa will highlight the military and diplomatic challenges for the US.

If ISIS is forced out of its Raqqa stronghold, which may happen in the coming year as the campaign to liberate Mosul intensifies, the US will want to minimise the risk of another weak, insecure and vulnerable Sunni entity arising in its stead. Whether it can achieve such an outcome will depend to some extent on the nature of the ground campaign that will be launched against ISIS. Who will contribute forces? Who might be willing to stay on, under whose auspices, and for how long?

The damage inflicted on Sunni rebel groups in Aleppo and elsewhere, and the unacceptability of working with al Qaida-backed elements, leaves the US with few options for launching a ground assault on ISIS other than some form of external Arab-Turkish intervention, or tacitly supporting the Assad regime's recapture of the ISIS 'capital'. But any Saudi attempt to launch a military offensive in conjunction with Turkey to secure a Sunni statelet in eastern Syria would be a direct challenge to the Kurds and Iranians. The fall of Raqqa to anti-Assad forces would also be seen as a threat to Aleppo, and ultimately to the regime's control of western Syria.

Recognising that an air campaign alone will not defeat ISIS, the US appears to be keeping open the option of an Arab-Turkish intervention to secure Raqqa. The reported US development of an advanced operating air facility as Hassakah in north-east Syria may be linked to that objective, as well as to the campaign for Mosul. Moreover, unlike the situation in western Syria, where the Russians are dominant, the air space over Raqqa is open to the coalition.

The Russians would face awkward choices responding to demands to provide close air support to regime (or Iranian or Kurdish) resistance to such an Arab-Turkish incursion. But Russia's primary interest is less in supporting the restoration of the Assad regime's authority across the whole of Syria than in making sure the regime is viable but also vulnerable to Russian pressure and responsive to Russia's interests and priorities. Moscow is more likely to focus on preservation of the Assad regime in western Syria while bargaining with the US over Raqqa and managing the disappointment of their clients (who irrespective of such Russian perfidy, would still depend upon Russian support elsewhere).

Whatever the exact nature of arrangements in Raqqa if ISIS was pushed out, the US will not wish to see any vacuum filled by forces equally inimical to American interests and values than ISIS or al Qaida.

Photo by Reuters/Anadolu Agency.