The British parliament's vote on 29 August 2013 against a motion giving effective permission for an early military attack on Syria set off a chain reaction in international decision-making and diplomacy. This took time to become clear, since at first Barack Obama's administration remained committed to action and had strong support from the French president, Francois Hollande. But Obama's decision to consult Congress, explicit concerns from retired senior military on both sides of the Atlantic, and strong public critiism combined to stall the momentum to war, showing that the House of Commons's vote had had an effect.
The Russian offer of a process to dispose of Syria's stock of chemical weapons, following United States secretary of state John Kerry's suggestion at a press conference that this was the only way to avoid intervention, then filled the space that had been opened. The negotiations now underway between Kerry and his Russian counterpart, Sergei Lavrov, mean that for the moment at least, the probability of armed confrontation with Syria is much diminished. The situation remains uncertain, however, and the danger most certainly has not gone away: Bashar al-Assad's regime may prevaricate in a way that brings crisis to the boil, or there may be one of those “AIM” events (accidents, incidents and mavericks) that can rapidly escalate.
In a longer-term perspective, the real question is whether this positive development in one aspect of Syria's war could be the start of more general progress. At first sight this looks unlikely, but there are reasons for a small measure of optimism.
The Russian factor
A key feature of the devastating civil war in Syria - as several columns in this series have argued - is that it is a double proxy war. This is clearest in the way that the Saudis and Qataris support the rebels with funding and armaments, while the Iranians and Hizbollah support Assad. At an even higher level, the Americans and some western European states back the rebels while the Russians back the regime.
Since the evolution of the war in the course of 2011, its the proxy nature has bedevilled any chance of externally mediated progress. This context alone makes the chemical-weapons agreement between Kerry and Lavrov a significant change. But whether the initiative can be turned into broad diplomatic pressure on the rebels and the Assad regime may depend on a particular feature of how the conflict has developed in 2012-13 - the rise of extreme Islamist elements among the rebel paramilitaries. These elements have become ever stronger, especially in northern Syria, to the extent of offering the most dedicated and effective opposition to the regime.
This is a major problem for the Obama administration, since its aid to the rebels risks enabling al-Qaida-linked paramilitaries to achieve power in the event of the regime's fall - or at least leaving parts of a post-Assad Syria in the hands of such groups. But the real measure of change, which so far is scarcely ecognised, is the new Russian predicament - for the more the Russians sustain a regime that is facing increasingly powerful Islamist opposition, the more this could affect Russia's own domestic security.
Since the Chechen wars of the late 1990s, Russia has faced a continual problem of violent Islamist opposition in the north Caucasus. In recent years this has been centred on a vigorous counter-terrorism operation against the "Caucasus Emirate". A conflict little reported in the western media has seen the Emirate conduct over 2,200 attacks, kill 1,500 Russian state officials and 400 civilians. Its campaign shows few signs of ending.
The host city of the winter Olympics of 2014 is Sochi, a Black Sea city on the western fringe of the north Caucasus. It is intended to provide an international showcase for Russia's president, Vladimir Putin. There are, though, plausible (if unconfirmed) reports of young paramilitaries from the region - from Chechnya and Dagestan in particular - joining some of the Islamist groups to fight in Syria. The possibility of a "blowback" is being taken very seriously.
In short, the United States may be deeply troubled by the prospect of Islamist paramilitaries active in a post-Assad Syria, but Russia has its own worries. The more Moscow supports Assad, the more Islamist propagandists can advance the idea that Russia is equally part of the “far enemy”. Thus, both Obama and Putin have a vested interest in a compromise that could end the war.
The missing link
Even good cooperation between the former cold-war adversaries, however, would leave in place the other ingredients of the double proxy. Iran and Saudi Arabia are in the forefornt here. In this respect too, there is some cause for optimism in that Iran's new president, Hassan Rowhani, is willing to engage with the United States. Tehran's calculation is that it is in Iran's interest to end the war by a negotiation which leaves its Hizbollah ally intact and constrains the rise of Sunni Islamists who see Iran as a nation of apostates.
But the position of Qatar and especially Saudi Arabia presents a difficulty to this evolving equation, for their support for Islamist rebels has a strong strategic basis. These states believe that Assad has to be defeated, as part of a wider war to prevent the establishment of a powerful Shi'a crescent stretching from the Mediterranean through southern Lebanon, Syria, Iraq and Iran to the Indian Ocean.
In this complex diplomatic process, the extent of Washington's influence with the Saudis may determine the chance of further advance. It may just be that previous experience, namely Rowhani's involvement in negotiating with the Saudis earlier in his career, may come into play - just as the Kerry-Lavrov relationhip has been important in the chemical-weapons negotiations.
Even taken together, all these factors offer only a small dose of optimism. Yet they cannot be discounted. If they do cohere and are built on, the UK parliament's decision on 29 August could yet be seen as a historic turning-point.