There is cause for both optimism and scepticism in the news that the US and Russia have agreed a ceasefire in Syria.
On the face of it, one of the world's bloodiest civil wars is about to come to an end — an end to be guaranteed by the two biggest, best armed militaries on the planet. This should be excellent news for everybody, not least the long suffering civilian population of one of the most bombed countries on earth.
The good news first. The Syrian Arab Army and the Kurds as well as their state backers should not fight each other.
The ceasefire announcement probably also forestalls Turkish and Saudi attacks against the government and the Kurds — both of which had either been threatened or were in progress. (The Turks have been shelling the Kurds and Syrian government for a week.)
Likewise, both sides commit to the political process. That includes adherence to the political process mandated in UN Security Council Resolution 2254 (including cessation of hostilities and a process leading to democratic elections).
Equally, the parties will allow aid to reach beleaguered areas. They also agree that they will work for the release of detainees.
These benefits cannot be underrated. While civilians have been used as a political football by all sides (both while there and once they have fled as refugees), there is no doubt they have been suffering. Once bustling, lively and ancient cities have been bombed, mined and booby-trapped. The inhabitants have been besieged, often for months, with limited access to food and water while living in the crossfire.
Even those living away from direct battlezones have been attacked — in the last days, dozens have been killed by car bombs in Homs and Damascus. Thousands have fled, meeting a mixed reception in places from Turkey to Nauru (from where three asylum seekers from Aleppo imprisoned by Australia have just found refuge in Canada).
So far so good.
So what could possibly go wrong?
Well, quite a lot. For a start, who is covered is unclear and open to a good deal of wrangling. The ceasefire covers 'any party currently engaged in military or paramilitary hostilities against any other parties other than 'Daesh', 'Jabhat al-Nusra', or other terrorist organisations designated by the UN Security Council'. In addition, persistent violators of the ceasefire will be treated as 'terrorists'.
The question of who else will or will not be treated as a terrorist group is much harder