The government of President Bashar al-Assad is resurgent in Syria, steadily retaking terrain lost to the rebels. This may bring to an end one set of conflicts, but it could spark newer, potentially more dangerous confrontations.

The key to preventing the Syrian civil war from splintering into an even more chaotic and deadly phase will be Russia, whose September 2015 military intervention gave it control of Syrian airspace and placed it politically in the driver’s seat. But the United States, too, could still play an important role in preventing matters from getting worse.

To understand how perilous the situation in Syria is, look at the map: In the northwest, in Idlib Province, a “de-escalation zone” that is monitored by the Turkish Army remains tenuous. The Assad government is keen to drive the Turks out, as well as jihadists and other rebels. In the northeast, the Kurds have established a form of self-government, led by the militia called Y.P.G., an American ally in the fight against Islamic State. But that group is the Syrian affiliate of the P.K.K. in Turkey, and is therefore in the Turkish military’s cross hairs. Further to the east, remnants of the Islamic State still roam the desert near the Iraqi border, pursued by the United States and the Y.P.G. as well as by the Syrian regime, and backed by Iran and associated militias.

The greatest danger lies in the south, along the armistice line that divides Israel and Syria. Recent tit-for-tat attacks between Israel and Iran and its allies have raised the risk of escalation. In February, only a phone call from President Vladimir Putin of Russia to Prime Minister Benjamin Netanyahu of Israel induced Israel to call off further airstrikes against Syrian government and Iranian targets after an Iranian drone invaded Israeli airspace. More recently, Israel piggybacked on international outrage over an apparent regime chemical attack to carry out a second round of strikes, reportedly killing 10 Iranian military personnel and several others at a Syrian airfield. Iran vowed to respond, and is likely to do so at a time of its choosing. This is a game of chicken that could easily spiral out of control.