When Syria's Kurdish fighters, America's longtime battlefield allies against the Islamic State, announced over the weekend that they were switching sides and joining up with Damascus and Moscow, it seemed like a moment of geopolitical whiplash. Fearing U.S. abandonment, the Kurds opened a back channel to the Syrian government and the Russians in 2018, and those talks ramped up significantly in recent weeks, American, Kurdish and Russian officials told The Associated Press. "We warned the Kurds that the Americans will ditch them," Russia's ambassador to the European Union, Vladimir Chizhov, told Russia's Tass news agency on Monday.