FILE - In this file photo taken Dec. 16, 2015 and provided by the Russian Defense Ministry Press Service, Russian S-400 long-range air defense missile systems are deployed at Hemeimeem air base in Syria. Russia's defense ministry said Tuesday, March 15, 2016, that the first group of warplanes stationed at the Russian air base in Syria has left for home following a pullout order from President Vladimir Putin. (Vadim Savitsky/Russian Defense Ministry Press Service via AP, File)