Abandoned by U.S. in Syria, Kurds Find New Ally in American Foe

Kurdish forces long allied with the United States in Syria announced a new deal on Sunday with the government in Damascus, a sworn enemy of Washington that is backed by Russia, as Turkish troops moved deeper into their territory and President Trump ordered the withdrawal of the American military from northern Syria.

The sudden shift marked a major turning point in Syria’s long war.

For five years, United States policy relied on collaborating with the Kurdish-led forces both to fight the Islamic State and to limit the influence of Iran and Russia, which support the Syrian government, with a goal of maintaining some leverage over any future settlement of the conflict.

On Sunday, after Mr. Trump abruptly abandoned that approach, American leverage appeared all but gone. That threatened to give President Bashar al-Assad and his Iranian and Russian backers a free hand. It also jeopardized hard-won gains against the Islamic State — and potentially opened the door for its return.

The Kurds’ deal with Damascus paved the way for government forces to return to the country’s northeast for the first time in years to try to repel a Turkish invasion launched after the Trump administration pulled American troops out of the way. The pullout has already unleashed chaos and bloodletting.