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.

In the West, Dmitry Medvedev was once seen as a democrat who could liberalise Russia. In a stunning fall, he has been reduced to a rabid attack dog for Vladimir Putin who threatens Western capitals with nuclear weapons and launches into xenophobic rants on social media.