President Donald Trump issued a rare threat of nuclear escalation on Friday, saying he had ordered two nuclear submarines to be strategically positioned near Russia in response to what he said were aggressive remarks by Dmitry Medvedev,

President Donald Trump has ordered the repositioning of two U.S. nuclear submarines. Friday's decision comes after what he calls "highly provocative statements" by former Russian President Dmitry Medvedev.

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.