The Syrian army joins the Kurds in a major shift in power.
The Syrian army entered the city of Tel Tamer in northeastern Syria, state news media reported on Monday, shortly after President Bashar al-Assad's government forged an alliance with the Kurdish forces controlling the region.
The government's return to northeastern Syria not only provides a blow to the Kurdish-led forces supported by the United States, but also signals a major change in Syria's eight-year war
The Syrian government had almost completely been absent from the northeast since it withdrew fight back or be chased out by armed rebels. The Syrian Democratic Forces, a Kurdish-led militia that worked with the United States to fight the Islamic State, soon became the region's overall political force.
President Trump's decision last week to move these troops out of the way of a Turkish invasion gave Mr. Assad an opening, and his forces began to fill it on Monday.
In some cities, they were welcomed by locals who sang nationalist slogans and carried Mr. Assad's photograph. In other areas, trucks drove a large number of Syrian soldiers into the area to take positions.
Tel Tamer is a strategic intersection linking northeastern Syria with the country's northern hub, Aleppo, and is 20 miles from the Ras al Ain center of the Turkish attack.
If Syrian government forces can reach the Turkish border in the north and the Iraqi border in the east, it would be a major breakthrough in Mr Assad's quest to restore his control over the entire country.
Syrian government forces also entered the city of Ain Issa on Monday, a day after it was briefly overrun by Turkish-led troops. About 500 ISIS sympathizers took advantage of the quay and escaped custody, local officials said.
Syria's state television showed long lines of Syrian army vehicles in Ain Issa on Monday, greeted by a group of cheering residents. "We've been waiting for you for a long time," one woman said.
A soldier held up his gun and said, "I'm here to kick out the Turkish mercenaries."
E.U. Foreign ministers agree to ban arm sales to Turkey.
Foreign Ministers from all 28 Member States of the European Union unanimously agreed on Monday to stop selling arms to Turkey, the first time the bloc made such a decision on a NATO ally.
In a joint statement by the foreign ministers, the bloc condemned Turkey's intrusion into northeastern Syria and agreed on strong wording despite the first concerns from the UK.
"The EU condemns Turkey's military efforts, which seriously undermine the stability and security of the entire region, resulting in more civilian suffering and further displacements and seriously impeding access to humanitarian aid," said the ministers.
The legal and practical aspects of such a move are complicated: Like most EU countries, Turkey is a NATO member. European officials decided that the best way to enforce the ban was by disabling arms sales licensing in individual European capitals, which made it a national feature.
This complexity was reflected in the joint statement: Citing earlier plans by France and Germany "to immediately halt the granting of arms export licenses to Turkey", the ministers said that "the member states are committed to strong national positions regarding their arms export policy to Turkey. "
The decision is expected to be most important for Germany, an important source of arms for Turkey. Britain, France and Italy also sell weapons to Turkey.
The Kurds are assisted by a new ally: Bashar al-Assad.
It has been only a week since President Trump withdrew American forces in Syria and effectively gave Turkey green light to cross the border and continue its own military agenda. Alliances change, ISIS is revived and thousands of civilian lives are threatened.
Embittered at the passing of their US allies, Kurdish leaders moved to secure a new partner: the government of Bashar al-Assad, a devoted enemy of the United States.
Late Sunday, Syrian Democratic Forces said they had reached an agreement with the Assad government that would allow government forces to enter the Kurdish-controlled northeast of Syria for the first time in years. The master of the S.D.F. wrote an article for foreign policy explaining the reasoning behind the deal.
The commander, Mazloum Abdi, said that in the absence of American assistance against the Turkish invasion, he had no choice but to seek help from the Syrian army and their Russian allies, although "we do not trust their promises."
"We know that we will have to make painful compromises with Moscow and Bashar al-Assad if we go to work with them," he added. "But if we have to choose between compromise and the genocide of our people, we will surely choose life for our people."
Trump administration officials once argued that keeping Assad's forces out of the territory was crucial to suing Iranian and Russian influence in Syria. But with US troops on their way out, Washington has lost its leverage.
"The worst in military logic and comrades in the shooter is storage," said an official ally with the Kurdish-led Syrian Democratic Forces.
Some US military members who had worked closely with the Kurdish militia were also scared.
"They trusted us and we broke that trust," said an army officer who has worked with the Kurds in northern Syria. "It's a stain on American conscience."
Turkey has promised to continue the offensive.
President Recep Tayyip Erdogan of Turkey on Monday said his troops would continue to support an invasion of parts of northern Syria, despite Syrian government forces returning.
Speaking at a news conference, Erdogan said a Turkish-backed force would press for attempts to capture Manbij, a city at the intersection of two major highways that the Kurdish authorities in northern Syria have been handed over to the Syrian government.
The invasion of Manbij would be led on the ground by Syrian Arab militias, but would have Turkish support, Erdogan said. The Turkish president seemed more ambivalent about Kobani, a Kurdish-controlled city on the Syrian border that Erdogan previously threatened to capture. It was the scene of a fierce battle between Kurdish warriors and ISIS extremists in 2014 and 2015 that ended in an ISIS retreat.
Mr. On Monday, Erdogan hinted that an agreement on Kobani had been reached with the Russian government, Syria's foremost international backer, although its significance was unclear.
"In Kobani with Russia's positive attitude, it seems there will be no problem," Mr Erdogan said without elaborating.
The official Turkish explanation for the offensive was to clear the area of the Kurdish-led militia that has close ties with a terrorist group banned in Turkey.
At the beginning of the invasion, Turkish officials said they respected Syrian sovereignty.
But on Monday, Yasin Aktay, an adviser to Mr. Erdogan, on Twitter said that "the fact that the Syrian Army has made an agreement" with the Kurdish militia "will not stop Turkey's counterterrorism operation. "
A second presidential adviser, Ibrahim Kalin, later tweeted that " Turkey will not stop until we reach our goals. "Turkish officials have previously promised to create a buffer zone along its border with Syria, about 20 kilometers deep.
The United States says that the Turkish strike near the US post was a mistake.
Turkish troops shelled within 550 meters of an American observation post in northern Syria late Friday while US troops were in the area, according to a military situation report obtained by The New York Times.
Since 2016, the United States has maintained several camps in northern Syria, including a post near the city of Kobani, as part of an international alliance fighting the Islamic State.
The military report undermines both US and Turkish stories of the shooting, first reported on Friday by Newsweek. In US news reports over the weekend, unidentified officials claimed in various ways that the Turkish shooting was probably intentional, that it was intense and that it had hit areas on both sides of the US post. In an official statement, the Pentagon said only that Turkish forces had shot down a few hundred meters of US troops.
In response, the Turkish Ministry of Defense said the strike was an accident and that its forces had fired on Kurdish troops about 1,000 yards from the US outpost. But the military progress report calls into question both the anonymous US information meetings and the Turkish account.
A map shows two Turkish artillery strikes two miles west of the US outpost and a strike landing approximately 300 to 500 meters southwest of the post, closer than the Turks acknowledged, but less intense than some US officials have claimed.
The military report said that the shooting near the US post was probably an accident and added that further misunderstandings from Turkish forces could not be ruled out.
Has Turkey opened the door to a revived ISIS?
The United States had no greater ally to expel Islamic State militants who claimed major battles in Syria in pursuit of a modern caliphate than the coalition of fighters known as Syrian Democratic Forces.
inch by inch, the Kurdish-led militia, working with its US military partners, drove ISIS militants out of their mounts.
But another U rited States ally viewed the militia much less fondly: Turkey. Its leaders looked across its southern border and did not see an ally but a threat to its territorial integrity, given the militia's ties to Kurdish separatists in Turkey.
With Turkish-led forces now threatening the Kurds, S.D.F. has turned the attention of the Islamic State, including the militants who were captured during the war and held in detention camps. Some ISIS members said they had already escaped, along with hundreds of their family members. A planned transfer of five dozen "high-value" prisoners to the United States from Syria never occurred.
Between escaped ISIS members and the Islamist sleeping cells believed to have been left behind when the militants were defeated in Syria, there is concern that the world has not seen the last of the extremist group.
Reporting was contributed by Carlotta Gall, Ben Hubbard, Charlie Savage, Eric Schmitt, Patrick Kingsley, Hwaida Saad, Matina Stevis-Gridneff, Anna Momigliano, Anton Troianovski, Eric Nagourney, Russell Goldman and Megan Specia.