Russia has abandoned a long-held nuclear "freeze" after Donald Trump deployed submarines near Vladimir Putin's coasts. Moscow has said it no longer considers itself bound by a self-imposed ban on the deployment of missiles - and is poised to bring short- and intermediate-range nuclear weapons into action.

The Kremlin has tried to calm tensions in a feud between Trump and Medvedev that spiraled into nuclear threats.

In 2017, during his first term as US president, Trump announced that he had sent two nuclear submarines to the Korean peninsula. Soon afterwards, he held a meeting with the North Korean leader, Kim Jong Un. Whether this latest move will lead to a new meeting with Putin is yet to be seen, however.