The content originally appeared on: CNN (CNN)John Sullivan, the United States' ambassador to Russia, has left his post and will retire, the US Embassy announced Sunday. Sullivan departs amid a period of heightened tensions between the US and Russia not seen in decades. He leaves after nearly three years as ambassador in Moscow, where he oversaw the embassy as it faced increasing restrictions imposed by the Russian government. 'U.S. Ambassador to the Russian Federation John J. Sullivan has concluded his […]