Former Russian president Dmitry Medvedev has become embroiled in a tense back-and-forth on social media that prompted U.S. President Donald Trump to announce he had ordered the re-positioning of two U.

“Putin uses Medvedev as a tool to express statements related to nuclear weapons, he doesn’t want to discredit his own good peacekeeper’s name,” Lieutenant-General Ihor Romanenko, former deputy head of the General Staff of the Ukrainian Armed Forces, said ironically.

The Kremlin tried Monday to defuse tensions caused by remarks from one of Russia’s top officials that led President Trump to shift two nuclear submarines closer to Moscow. “As you know, Russia holds a responsible position.