QAMISHLI, Syria — As United States troops continued their withdrawal from Syria on Sunday, a line of cars carried their routed former allies, terrified civilians and dead bodies out of a pulverized border town that had been besieged by Turkish forces for more than a week.
Away from the front lines where the Turks might assassinate him, the Kurdish leader of the Syrian force that once helped America battle the Islamic State, and that has now been abandoned by the Trump administration, looked drained from 10 days of battle and geopolitical struggle over his people’s fate.
The commander, Mazlum Kobani, had visibly lost weight, and his eyes drooped from exhaustion. His fighters had shed considerable blood to wrest territory from the Islamic State and establish self-rule on its former lands. Now, he worried that a complete American withdrawal would not only jeopardize those gains but also subject his people to displacement and slaughter.
“There will be ethnic cleansing of the Kurdish people from Syria, and the American administration will be responsible for it,” said Mr. Kobani, commander of the Syrian Democratic Forces.
But if he felt any bitterness that the Americans his fighters had battled alongside for years were now running for the exits, he did not show it, instead expressing hope that the partnership could live on.
“America needs to work to rebuild the trust with its ally against ISIS,” Mr. Kobani said. The United States should work, he said, “to limit the damage of this past decision and preserve the areas we liberated together.”
The Turkish incursion into northeastern Syria to sweep Mr. Kobani’s forces away from the border followed President Trump’s decision to pull American troops out of the way. That decision shattered what had been a fragile peace, setting off fighting that has killed more than 200 people.
On Sunday, the clashes had mostly stopped but fear still coursed through northeastern Syria, with residents unsure whether the Turks or the government of President Bashar al-Assad would soon take over the area. People wounded in the fighting filled hospital wards.
American and Turkish officials agreed to a cease-fire on the border late last week and the establishment of a “safe zone” for civilians, but few seemed reassured on Sunday.
“It is going to be chaos,” said Abdulqader Omar Nabi, 46, who fled the border town of Ras al-Ain after his home was destroyed by a Turkish airstrike. “It won’t be a safe zone. It will be destroyed.”
His son, Shiyar, who came out of the town with other wounded residents on Sunday’s convoy, said he feared the Syrian fighters who are being backed by the Turks.
“They don’t see any difference between fighters and civilians,” he said. “If you are a Kurd, they’ll kill you.”
Mr. Kobani finds himself at the center of a swirl of forces seeking a stake in the region.
The Syrian government wants to reclaim territory that Mr. Kobani’s forces control and has sent troops to keep the Turks from advancing. Russia has stepped in to broker deals. Turkey has dispatched Syrian militias to take territory. And the Trump administration announced a cease-fire deal last week that would allow Turkey to establish a so-called “safe zone” in Syria where it hopes to resettle Syrian refugees.
Turkey moved one step closer to that goal on Sunday when hundreds of Mr. Kobani’s fighters and haggard civilians finally left the border town of Ras al-Ain, which Turkey and its Syrian proxies had heavily bombarded.
“It has been evacuated,” said Mr. Kobani, a nom de guerre. “There is no one left. It’s over.”
Under the cease-fire agreement, reached by Vice President Mike Pence and President Recep Tayyip Erdogan of Turkey on Thursday, Mr. Kobani’s fighters are to leave a rectangular piece of territory that is bounded by the towns of Tel Abyad and Ras al-Ain on Syria’s border with Turkey, and runs south to a main highway in territory Mr. Kobani’s forces control, by Tuesday night.
Since the agreement was announced, both sides have accused each other of violations and described its terms differently, raising the possibility that it could break down.
A joint communiqué released by the United States and Turkey said that Turkey was responsible for ensuring the “safety and well-being of residents” and that Turkish forces would control the area.
But on Sunday, Mr. Kobani said that he had not agreed to allow a “Turkish occupation” of the zone and that he feared the changes one might bring.
“There need to be red lines: that the Turks can’t do ethnic cleansing or demographic change, about how they will deal with the people there, about permanent Turkish control over the area,” he said. “We will not accept these things.”
Mr. Kobani’s power came from the S.D.F.’s partnership with an international coalition led by the United States to fight the Islamic State. As the jihadists were pushed back, his forces seized more territory, which a contingent of about 1,000 American troops helped them control.
That partnership angered Turkey, an American ally in NATO, because Mr. Kobani’s fighters had links to a Kurdish guerrilla movement that has been fighting the Turkish state for decades. Mr. Erdogan had long threatened to push Kurdish forces away from the border, saying it was necessary for Turkey’s security.
Mr. Trump’s decision to pull United States troops out of the way of a Turkish advance and to begin withdrawing them from Syria deprived Mr. Kobani of his strongest backer and left him scrambling to reach new accommodations with the region’s other powers. This has put him in touch with a surprising number of powerful people for a man who heads a relatively unknown militia in an obscure corner of Syria.
Since the violence started, he has met with senior aides to President al-Assad of Syria, whom the United States considers a war criminal; spoken with top brass from the Russian military, which backs Mr. al-Assad; and had phone calls with prominent Americans like Senator Lindsey Graham of South Carolina, who opposes Mr. Trump’s decision to pull out of Syria. On Saturday he talked to Mr. Pence, and he spoke with Mr. Trump last week.
“The issues are very complicated,” Mr. Kobani said. “I meet with everyone, and I will make any decision that is in our people’s interest.”
On Sunday, he said he had been invited to visit Washington but declined to say by whom or when he might go.
“The issue is serious,” he said. “But everything in its time.”
The timing and scale of the United States withdrawal from Syria remains unclear. Mr. Trump may leave only a contingent of 150 troops at an isolated base in the south, or he may leave those plus some others in the east.
Mr. Kobani is hoping for the larger deployment. His fighters, he said, need American help to prevent the Islamic State from reconstituting.
Of particular concern to Mr. Kobani are Syrian proxy militias that Turkey has backed to fight his forces in Syria.
Many of them are virulently anti-Kurdish and have reputations for looting and criminality. As the fighting began last week, one group killed at least two Kurdish captives and a female Kurdish politician.
On Sunday, the commander of one of those groups said they expected to deploy inside the cease-fire zone after the agreement ends Tuesday night. The commander, Abdulaziz Jamil, acknowledged bad behavior by some Turkish-backed groups.
“There are some violations by some factions on the ground, like looting people’s properties, which is really bothering me a lot,” he said.
Many residents from the proposed safe zone fear that the presence of such groups will make it anything but safe.
Also on Sunday, the House speaker, Nancy Pelosi, traveled to Jordan to meet the Jordanian king for discussions about the Turkish incursion into Syria and other regional challenges.
Ms. Pelosi, a California Democrat, led a nine-member congressional delegation to Jordan that included Representatives Adam Schiff, Democrat of California; Eliot L. Engel, Democrat of New York; and Mac Thornberry, Republican of Texas. The group met with King Abdullah II of Jordan.
“With the deepening crisis in Syria after Turkey’s incursion, our delegation has engaged in vital discussions about the impact to regional stability, increased flow of refugees, and the dangerous opening that has been provided to ISIS, Iran and Russia,” Ms. Pelosi’s office said in a statement.
Patrick Kingsley contributed reporting from Istanbul, and Hwaida Saad from Beirut.