Last Friday, Serbian Prime Minister Aleksandar Vucic made an unannounced visit to Moscow. The trip came amid reports of Russian concern with Serbia’s overtures to the West, including taking steps toward joining the European Union.

Later that day, Russian President Vladimir Putin headed to Greece, where he discussed energy cooperation and investment with Greek Prime Minister Alexis Tsipras, before visiting the male-only Monastery of St. Panteleimon on Mount Athos with the head of Russia’s Orthodox Church. The trip was Putin’s first to an EU country this year, as the debate heats up in Brussels over renewing EU sanctions against Russia for its annexation of Crimea and destabilization of Ukraine. ...