Syria's "cessation of hostilities" is making a difference - whatever the arguments about early violations, the level of violence across the country has fallen - and with this fragile modicum of progress, the United States and Russia find themselves in harness after years in which Syria was a forum for their rivalry.
"My worry is that it is the Russians making the weather," says Lieutenant General Sir Simon Mayall, senior Middle East adviser at the UK Ministry of Defence until last autumn.
"It was in their gift to offer a ceasefire on behalf of the Assad regime. That slightly worries me in a part of the world where the Americans have been the guarantors and the people who make the weather."
Following on from the Munich agreement of earlier this month, Russia and the US have become co-chairs of the International Syria Support Group working parties dealing with the implementation of humanitarian supplies, as well as the deal under which President Bashar al-Assad's forces and groups of the "non-terrorist opposition" are meant to stop shooting at each other.
Both powers have worked hard to deliver this deal, and both now have a vested interest in its success.
"They are co-owners, insofar as the Russians respect the political process, and do apply pressure on Assad to stop bombing and take the process seriously," says Karin von Hippel, until recently a senior State Department official dealing with US strategy against the so-called Islamic State (IS) group, and now director general of the Royal United Services Institute think-tank.
Washington regards rapid progress towards political talks between the Assad government and the High Negotiations Committee (HNC), an umbrella group of his opponents, as essential.
Russian airpower
But privately officials are nervous, both about Russian attempts to brand any group that has ever co-operated with militant elements like IS or the al-Qaeda-affiliated Nusra Front as "terrorist" and, therefore, ineligible to take part in, or make any significant move towards moving President Assad off the political stage.
As the US has pressed ahead with its Russian partners, the whispering has started in London or Paris about how John Kerry, US Secretary of State, has allowed himself to align with a Russian plan to keep Mr Assad in power indefinitely.
The US has conceded publicly that the Syrian leader can stay "for now", and it's clear also that they have used considerable pressure to compel their allies to go along with the Munich agreement.
In the run up to Munich, both Syrian opposition and European sources were saying that Mr Kerry had threatened the HNC with a complete aid cut-off unless they went along with the peace process.
As Syrian government and allied forces, backed by Russian airpower, advanced north of Aleppo early in February, both Turkey and Saudi Arabia looked set to intervene in defence of rebel groups they have been supporting.
On 11 February, for example, Saudi MoD spokesman Brigadier Ahmed al-Assiri, said his country had taken a "final" and "irreversible" decision to send ground troops to Syria in order combat the so-called Islamic State. Turkish forces, meanwhile, were shelling Syrian Kurdish groups, and were accused by Russia of preparing to invade their southern neighbour.
Syrian partition?
This mid-February crisis, which could have put Russian forces supporting President Assad on a collision course with those of Nato-member Turkey or seen a ground push into eastern Syria by the Saudis passed, thanks to US pressure on its allies.
Speaking to journalists on Monday, Brigadier al-Assiri said: "If there is any consensus around ground troops in Syria, we will be in the front line."
Instead of sending ground troops, Saudi Arabia has, for the moment, contented itself with deploying a handful of jets to Turkey to carry out strikes on IS.