A force that helped defeat Islamic State is collapsing as the Trump administration turns to back the new Syrian government

For more than a decade, they were the United States’ closest allies in Syria, fighting against the Islamic State group, guarding US bases and running internment camps and prisons that held tens of thousands of jihadis and their relatives.

That alliance is now disintegrating. The United States has turned away from its long-time allies, the Syrian Democratic Forces, or SDF, and thrown its support behind the new government of President Ahmad al-Sharaa.

Without US backing, the SDF, a Kurdish-led force, has wobbled and beaten a retreat as the government moves troops into northeastern Syria to seize control, ending a standoff that has endured since al-Sharaa took power in December 2024.

The collapse of the SDF marks a turning point in Syria’s political transition after the fall of President Bashar Assad and now paves the way for the government to take over the strategic region, its oilfields and rich agricultural lands.

The pivot by Washington is a huge win for al-Sharaa, who has struggled to pull the country back together, as well as for Turkey, which vehemently opposed US support for the SDF and backed al-Sharaa.

But for the SDF and its supporters, including US officials who worked closely with the group, it feels like a betrayal of those who fought loyally alongside the United States and lost many thousands of combatants in the process.

The SDF was born following the terrifying rise of the Islamic State group, which took over a swath of territory straddling the Syria-Iraq border in 2013 and built a so-called caliphate on a harsh interpretation of Islamic law and and sheer brutality.

Seeking a way to fight the group without putting US troops on the front lines, the United States partnered with a Kurdish militia. It airdropped weapons to help break the siege of the Kurdish town of Kobani in 2014 and the partnership developed from there.

For the US, it made sense. The fighters were well-trained, not Islamist and eager to work with US troops. In time, with US financial and military support, they grew, added Arab fighters and rebranded themselves as the Syrian Democratic Forces (although there was very little about them that was actually democratic).

With logistical and air support from the United States and others, the SDF destroyed the Isis caliphate, pushing the group from its last patch of territory in Syria in 2019.

It continued to work with the United States to prevent the resurgence of Isis and provide security across northeastern Syria with a force of tens of thousands of men and women under arms.

That alliance angered Turkey, which saw the group as no more than an extension of the Kurdistan Workers’ Party, a Kurdish militant group that has fought a bloody, 30-year insurgency against the Turkish state.

It also angered Syrian rebel groups and activists for imposing Kurdish rule over Arab-majority areas and doing its own deals with the Assad regime.

The rebel offensive that toppled the Assad regime in December 2024 changed the paradigm for the Kurds. The United States established close ties with al-Sharaa and sought to bring the two groups to work together.

US ambassador to Turkey and envoy for Syria Tom Barrack led the negotiations and secured an agreement between al-Sharaa and the Kurdish leader of the SDF, Mazloum Abdi, in March 2025.

But those negotiations stalled and missed the deadline for SDF to integrate its armed units and administration into the Damascus government by the end of 2025.

Al-Sharaa complained that the Kurdish side kept augmenting its demands while making no move to withdraw from Arab-majority areas. The Kurdish leaders said they were holding out for security guarantees for their people in light of sectarian killings elsewhere in Syria.

In the end, al-Sharaa lost patience and moved to seize control of two Kurdish-held neighbourhoods in the city of Aleppo. From there, Syrian forces moved rapidly, securing two large provincial capitals, Raqqa and Deir el-Zour, in recent days.

Newaf Xelil, an analyst at the Berlin-based Kurdish Center for Studies, said the swift advance of al-Sharaa’s forces in recent weeks had been enabled by the full embrace of his government by Turkey, Saudi Arabia and the United States.