Achieving a general ceasefire in Syria has been central to every diplomatic initiative to end the conflict since the United Nations Security Council issued a presidential statement endorsing what was known as the "Kofi Annan plan" in March 2012. But getting the combatants to comply was never going to be easy, not least because their external backers were not prepared to go far enough to make them do so.
The ceasefire brokered by Russia and Turkey on December 29, 2016, is no different. But this time the stakes may be high enough to force Russia's hand, opening an avenue towards more effective diplomacy, albeit geared to more modest objectives than reaching a full peace deal.
Russia has arguably sought a political settlement from the outset of its military intervention in Syria as a means both of securing a return on its investment in the Assad regime and of consolidating its claim to global power status. With Turkey now on board and bringing most of Syria's political and armed opposition with it, the main obstacle to Russian aims is the Assad regime and, behind it, Iran.
Visibly buoyed by its success in taking full control of Aleppo, the regime appears determined to subdue remaining opposition enclaves around Damascus. This prompted the armed opposition groups that had signed on to the latest ceasefire to announce it at an end on January 9, 2017. For its part, Iran refrained from sponsoring the ceasefire, although it had joined Russia and Turkey just nine days earlier in the "Moscow Declaration" calling for a truce and peace talks.
Does Russia have the influence to sway either of its allies? If not, can it afford to simply stay its current course in Syria, providing combat support indefinitely to a regime that has no real prospect of resolving severe challenges of political stability and economic regeneration even if it attains its much-vaunted "total victory" through military means?
Enforcing the ceasefire
In sharp contrast to past ceasefire agreements, Russia and Turkey have given their version some teeth by endorsing the principle of "imposing sanctions on violating parties".
Their precise form remains under discussion between the two guarantors, as Turkish Foreign Minister Mevlüt Cavusoglu confirmed on January 5, and may prove too difficult to finalise. Russia is unlikely to accept Turkish and opposition demands to make the Syrian army equally liable to sanctions, and even less to approve Cavusoglu's suggestion of seeking a further Security Council resolution formalising them.
Russia faces a moment of truth in 2017: It must be ready to go to considerably greater lengths to compel the Assad regime to engage politically, or to go home.
But Russia has signalled a potentially important shift simply by endorsing the idea of enforcement, as well as agreeing to joint monitoring on the ground by Turkish and Russian observers. Its air strikes supporting the Turkish-backed Euphrates Shield force battling the Islamic State in al-Bab on December 30, 2016, were also significant: although clearly intended as a positive gesture towards Turkey, they are the only instance in the entire Syrian conflict of direct air support by any power for the armed opposition.
And by announcing the withdrawal of its aircraft carrier group from Syrian waters on January 6, 2017, on the grounds that it had completed its mission, Russia signalled its readiness to scale down combat operations to the regime.
Russia has other, non-lethal options for ratcheting up its political pressure on Bashar al-Assad. It has already enhanced the status of seven of the most important armed formations by treating them as an opposition leadership, and withdrawn its previous rejection of several of them as "terrorist" organisations.
Russia has also entertained Turkish and opposition proposals to engage with local administrative councils in opposition-held areas; these mesh with draft Russian proposals for decentralisation of power in Syria floated since last March, and if implemented would open the way for future provision of humanitarian assistance and economic aid for rebuilding.
Of course, little of this will be put to the test so long as Assad continues to reject these proposals outright. He may, moreover, expect to be let off the hook once US President-elect Donald Trump is sworn in, leaving him little reason to submit to Russian pressure.
Iran probably expects to be targeted by the incoming US administration, and consequently will be even less willing to relinquish its position in Syria. For these two allies, Russia has already run out of time to bring about its preferred outcome there.
Russia faces a moment of truth in 2017: It must be ready to go to considerably greater lengths to compel the Assad regime to engage politically, or to go home. It is likely to do neither, but cannot afford to remain stuck instead with an ongoing military commitment and no political strategy, having surrendered the latter to Assad and Iran.
A more sensible alternative would be to focus on reinforcing the ceasefire and elaborating effective monitoring mechanisms, increasing contacts with the armed and political wings of the Syrian opposition, and helping Turkey, United Nations agencies, and other international partners to assist basic public services and infrastructure in opposition areas.
This could improve chances for eventual peace-making, but at worst it cannot harm them.
Yezid Sayigh is a senior associate at the Carnegie Middle East Centre in Beirut.
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.