The 13-year civil war between Syria’s government and rebel fighters has ended. But the peril is not over for Syria’s Kurdish minority.

A number of armed factions are still jostling for control after the collapse of the Assad regime. They include the Kurdish-led Syrian Democratic Forces, which have allied with the United States to combat the extremist Islamic State, and the Syrian National Army, a militia backed by Turkey, which is hostile to the Kurdish forces.

For more than a decade, the Kurdish-led soldiers have been America’s most reliable partner in Syria, liberating cities seized by the extremist group and detaining around 9,000 of its fighters.

But Turkey, which shares a border with Syria, has long considered the Kurdish group to be its enemy. The Turkish government believes the Kurdish fighters in Syria are allied with the separatist Kurdistan Workers’ Party, or P.K.K., which has fought the Turkish state for decades.

President Recep Tayyip Erdogan of Turkey, who backs the rebel groups that toppled the Assad regime, appears eager to seize the opportunity created by the momentous political shift in Syria to pursue his own agenda against the Kurdish fighters.