Putting aside the unfortunate historical ring to “peace” agreements signed in Munich, today’s Syrian truce is deeply flawed and unlikely to hold for long. The “cessation of hostilities” – for it is not a true ceasefire – has been hailed as a landmark piece of diplomacy that brings some respite to a war that long ago spiralled out of control.

The veteran diplomat Lord Williams told the BBC: “In a cold war fashion, the two superpowers have taken ownership of the problem.” In fact, it is the US and Europe that appear to own the problem, while Russia has held tight to the solution. Washington, wielding words, has few credible means of enforcement against Moscow, wielding unguided, though effective, bombs. This is why the truce includes loopholes large enough to fly a few dozen Russian jets through.

The statement by the International Syria Support Group (ISSG), a contact group of 17 countries on both sides of the civil war, agreed “a nationwide cessation of hostilities”. But an exemption was carved out for Isis, Jabhat al-Nusra (al-Qaida’s Syrian branch) and “other groups designated as terrorist organisations by the United Nations security council”. This sounds reasonable. However, both Russia and Iran – which has mobilised and led the ground forces operating under Moscow’s air cover – consider virtually all Syrian rebel groups operating around Aleppo, the site of the past week’s fiercest fighting, to fall into this expansive category.

The truth is more complicated. In the strip of rebel-held territory between Aleppo and Turkey, al-Nusra is indeed a powerful force. But it operates as part of a larger Turkish and Saudi-backed rebel coalition, Jaish al-Fatah, which also includes less extreme, though still ultraconservative, Islamist groups. The most significant of these is Ahrar al-Sham. It is these groups, and not Isis, that represent the bulk of targets in the Russian campaign, notwithstanding the Kremlin’s propaganda.

Washington, Ankara, Riyadh and Doha don’t completely agree on how this middle ground of Islamists should be handled. The US understands that their views are in tension with the civil, pluralistic Syrian state that must follow Bashar al-Assad. Saudi Arabia and Turkey don’t really care. But no one wants them bombed. Isis might exploit the vacuum, and it would bind the less extreme groups more tightly to their sometime al-Nusra collaborators.

The Munich truce says that an ISSG taskforce co-chaired by Russia and the US will “delineate” Isis and al-Nusra territory and resolve disputes that arise later. But groups are intermingled on the battlefield in the complex suburban geography of Aleppo and its environs, and the affiliations of individual battalions can be fluid.

Russia’s spectacular battlefield gains in the past month make it less inclined to accommodate American or Saudi preferences. And its offensive is doubly advantageous: not only is Assad winning, but the ensuing refugee flow leaves Europe even more desperate to make the problem go away, whatever the price. Moscow may therefore simply ignore these procedural niceties, and the US might be inclined to go along with this.

After all, the US secretary of state, John Kerry, speaking alongside his Russian counterpart today, stated emphatically that “it was not Russia or Iran who stopped a ceasefire from being adopted at the very beginning. I want to make that very, very clear.” This was a remarkable, stinging attack on Saudi Arabia and Turkey. These countries had indeed worried that a ceasefire without a parallel political transition away from Assad would freeze the status quo, leave the regime permanently in place and therefore help Isis to thrive.

Over the past week, the rebels’ increasingly wretched position – the very real sense that they might, simply, be obliterated – and the US’s unwillingness to push back seemed to have persuaded these powers to back the ceasefire. But Kerry’s remarks – exculpatory towards Moscow and Tehran, and implicitly censorious of the US’s own allies – will deepen Turkey and the Gulf states’ gloom at the changing balance of power and influence in the region.

It will also be interesting to see how the truce affects the relationship between Russia and its Syrian client. Less than a week ago, one of Assad’s senior advisers, emboldened by the military turnaround, insisted that suggestions of a ceasefire were the work of states that “do not want an end to terrorism” and merely wanted to aid rebels. Yet Assad could do little but accept the deal cut over his head. His army is in tatters, with Russia doing the bombing and Iran-led forces largely doing the fighting. His regime has been saved, but he will be nervous about his impotence over diplomacy that could affect his personal future.

Russia is unlikely to forgo its military momentum. It has every hope of not only cutting rebels off from their Turkish supply lines, but perhaps also retaking regime territory elsewhere. If Aleppo, why not Palmyra? Writing on Wednesday, Vitaly Naumkin, a Russian academic closely involved in Syrian diplomacy, suggested that the regime’s goals include the “establishment of a bridgehead for a massive offensive on [Isis] strongholds in the east”. This process could be less problematic in places where Isis is the only real opposition, but in other, less clear-cut battlefields – around Deraa in the south, for instance, we will have renewed spats over who is a terrorist and who is not.

Kerry clearly hopes that this truce will be a stepping stone to a broader ceasefire. Today’s ISSG statement reiterates the lofty aim of an agreement on political transition – to include elections and a new constitution – within six months. But if Russia is bent on a military solution, it will pocket the gains of this agreement. As pressure in Syria’s north eases and regime control spreads, the incentives to push out Assad and reform the regime shrink. Truce and talks should have come as a package. Instead, Russia has given up a little and gained a lot.