Nuclear sub moves should not be announced on social media

These are heavily armed vessels whose real positions are top secret

- James Stavridis

Over the last week, two political leaders have exchanged barbs underlining the powerful nuclear arsenals of their respective nations. It was not just a pointless demonstration of bravado, it also showed that careless words and vague military threats can move the world closer to a disastrous conflict.

The first to lash out was Dmitry Medvedev, Russia's former president who now serves as deputy chair of President Vladimir Putin's security council. In a social media post on 28 July, he said a US ultimatum for Moscow to come to the negotiating table over Ukraine was a "threat and a step towards war." Later, he alluded to Russia's "dead hand" nuclear launch system, which automatically fires a nuclear strike if the nation is attacked with such weapons.

US President Donald Trump responded to Medvedev by saying he had ordered two nuclear submarines "to be positioned in the appropriate regions." He also said, correctly, that "words are very important and can often lead to unintended consequences, I hope this will not be one of those instances." Later, a Kremlin spokesman warned against "nuclear rhetoric."

Between them, the US and Russia have more than 10,000 nuclear weapons. How dangerous is this war of words between the Kremlin and the White House? And what is the significance of Trump's nuclear submarine claim?