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– His jets patrol Syrian skies. His military is expanding operations at the main naval base in Syria. He is forging closer ties to Turkey. He and his Syrian allies are moving into territory vacated by the United States.

And on Tuesday, President Vladimir Putin of Russia played host to President Recep Tayyip Erdogan of Turkey, for more than six hours of talks on how they and other regional players will divide control of Syria, a land devastated by eight years of civil war.

The negotiations ended in a victory for Putin: Russian and Turkish troops will take joint control over a vast swath of formerly Kurdish-held territory in northern Syria, in a move that cements the rapid expansion of Russian influence in Syria at the expense of the U.S. and its Kurdish former allies.

Under terms of the deal, Syrian Kurdish forces have six days to retreat more than 20 miles from the border, abandoning land that they had controlled uncontested until earlier this month — when their protectors, the U.S. military, suddenly began to withdraw. The Syrian Kurdish leadership did not immediately respond to the demand.

Erdogan got most of what he wanted — a buffer zone free of a militia that Turkey regards as a terrorist threat — but it came at the expense of sharing control of the area with Putin and Syrian President Bashar Assad, whose rule Erdogan has long opposed.

“Only if Syria’s sovereignty and territorial integrity is respected can a long-lasting and solid stabilization in Syria be achieved,” Putin said alongside Erdogan after the meeting. “It is important that our Turkish partners share this approach,” Putin added. “The Turks will have to defend peace and calm on the border together with the Syrians. This can only be done in the atmosphere of mutual respect and cooperation.”

Putin has emerged as the dominant force in Syria and a major power broker in the broader Middle East — a status showcased by Erdogan’s hastily arranged trip to the Russian president’s summer home in Sochi. And it looks increasingly clear that Russia, which rescued the government of Assad with airstrikes over the past four years, will be the arbiter of the power balance there.

As President Donald Trump questions U.S. alliances and troop deployments around the world, Russia, like China, has been flexing its muscles, eager to fill the power vacuum left by a more isolationist United States. In Syria, both Putin and Erdogan have seized opportunities created in Trump’s sudden withdrawal this month of U.S. forces in the country.

Erdogan had long wanted to go to war against the Kurdish-led forces that control northeast Syria, but he dared not, as long as the Kurds’ U.S. allies were stationed there, too. He responded to Trump’s withdrawal by launching an invasion.

The Sochi meeting began a few hours before the end of a U.S.-brokered truce between Turkish and Kurdish forces in Syria, where Erdogan says his troops have seized more than 900 square miles of territory since invading Oct. 6.

“The U.S. is still the 500-pound gorilla,” said Howard Eissenstat, a professor of Middle East history at St. Lawrence University in Canton, N.Y. “If the U.S. decided that ‘issue X’ was a primary concern to its national security, there would be very little that anybody in the region could do about it.”

But with the U.S. increasingly removing itself from the picture — as symbolized in the Russian news media by the images of abandoned washing machines and unopened cans of Coca-Cola left behind in the chaotic withdrawal — it was Russia’s consent that Erdogan needed Tuesday to solidify and extend his gains.

“Before, Turkey could play the U.S. against Russia and Russia against the U.S.,” said Sinan Ulgen, chairman of the Center for Economics and Foreign Policy Studies, an Istanbul-based research group. “Now that’s no longer the case, and Russia has shaped up to be Turkey’s only real counterpart in Syria.”

The Sochi meeting looked to be a culmination of Putin’s yearslong strategy of taking advantage of Western divisions to build closer ties with Turkey — a NATO member and long a key U.S. ally — and to increase Moscow’s influence in the Middle East.

As the U.S. and Western Europe vacillated in their approach to Syria — to the frustration of Turkey and other Middle Eastern powers — Russia chose to protect its ally, Assad, and stuck with him despite fierce criticism from the West that the Syrian ruler was a brutal despot.

The upshot, Russians now say, is that while their country lacks the West’s economic might, it can be counted on to keep its word.

Assad attempted to project his own influence Tuesday, visiting the northwestern Idlib Province for the first time since the area fell out of government control several years ago.