Islamic State militants have taken territory from US and Turkish-backed Syrian rebels in an ongoing offensive, and now threaten a key rebel supply line from the Turkish border.
Diplomats and Syrian factions say the ceasefire will not collapse as long as the US and Russia support it, but the fighting is actually intensifying in some places.
Syria's ceasefire is shaky, but, for the most part, holding, thanks to an international effort that has been more successful than anyone ever thought possible.
At midnight Saturday, a truce brokered by the US and Russia goes into effect, but not in areas where "terrorists" are. And we don't know who gets to call whom a terrorist.
The newest allies of the US are battling the old ones, Russia keeps bombing, the regime's army advances, and the Islamic State sits back while its enemies kill one another.
With the decisive help of relentless bombing from the Russian air force, the army of Bashar al-Assad may soon choke off a key supply route for rebels in Aleppo, Syria's biggest city.
The UN envoy for Syria called a halt to the negotiations after days of trying to get the Assad regime and the opposition to agree on what they wanted to discuss in the first place.
Syrian rebel brigades and religious scholars have issued calls for all able-bodied Muslim men to join the fight against the Assad regime and its allies.
With Russia and Iran's help, the regime is laying siege to key towns in the areas where most of the Syrian people and economy are. That's good for Assad, and bad for the rebels.
Turkey is outsourcing the job of pushing back the Islamic State to rebels based in Syria's east. And, according to those rebels, it's an approach that's beginning to work.
The Syrian opposition came together for a conference in Saudi Arabia this week — but the pullout of a key player means real peace talks aren't happening just yet.
The New Syrian Army has American weapons, support from coalition airstrikes, and a deep-seated hatred for IS. But it's still too small to try and liberate the key province of Deir al-Zour.