Moving nuclear subs not something to announce on social media

Submarines are the apex predators of the oceans. They're not sabre-rattling tools, especially when the US and Russia have over 10,000 nuclear weapons between them.

- James Stavridis

Over the past 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 Mr Dmitry Medvedev, a former president and prime minister of Russia, who now serves as deputy chairman of President Vladimir Putin's security council.

In a social media post on July 28, 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 Mr Medvedev's comments by saying he had ordered two nuclear submarines "to be positioned in the appropriate regions". He concluded by saying, correctly, that "words are very important and can often lead to unintended consequences" and that he hoped "this will not be one of those instances". (On Monday, a Kremlin spokesperson 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 White House and the Kremlin? And what is the significance of Mr Trump claiming to have moved nuclear submarines to new stations?