Donald Trump deployed nuclear submarines towards Russia - Petty Officer 2nd Class Kelsey Hockenberger/Public Domain

In normal times, this would be an extraordinary, epoch-changing and terror-inducing moment.

Never before has a US leader chosen to engage in nuclear brinkmanship of this kind.

True, the Soviet Union famously triggered a nuclear showdown in 1962 by moving nuclear warheads to within 90 miles of the US shoreline during the Cuban Missile Crisis. For 13 days, the world feared Armageddon.

A Cuban Missile Crisis Mark II, this quite patently is not.

Yet, that does not mean that what the US president has just done is risk-free.

He has shifted Washington’s nuclear posture towards Russia in a way that none of his predecessors dared, climbing – almost casually – the first rung of the nuclear escalation ladder.

Should Vladimir Putin choose to respond in kind, a major crisis could follow.

That seems unlikely – a calculation Mr Trump has presumably made. In fact, he appears to be borrowing from the Russian playbook.

The deployment status of nuclear submarines is normally kept secret - Bryan Tomforde/US Navy

Putin has long used nuclear posturing as a tool of coercion. During bouts of tension with the West, he has deployed Iskander missiles, capable of firing nuclear warheads, to the exclave of Kaliningrad on the border with Poland, a Nato member.

In 2023, he stationed tactical nuclear weapons in Belarus – the first time since the Cold War that Russia has placed nuclear weapons outside its own territory. He has also repeatedly hinted at using a tactical weapon in Ukraine.

And on Friday, Putin announced that Russia had started producing Oreshnik hypersonic intermediate-range missiles, reaffirming plans to deploy them to Belarus this year. He boasted he had already selected sites for their deployment.

In recent days, Dmitry Medvedev, the former Russian president and now Putin’s social media attack dog, who has previously rattled the nuclear sabre, warned that Mr Trump’s threats could spark war between the US and Russia.

Donald Trump described Dmitry Medvedev as the ‘failed former president - Eric Lee/Bloomberg Finance LP

Mr Trump, who has recently tempered his admiration of Putin, made it clear that he was calling Russia’s bluff. In so many words, he told Moscow he was taking its threats literally rather than figuratively – an inversion of the advice his supporters usually give about him.

He wrote in a social media post directed at Mr Medvedev: “Words are very important, and can often lead to unintended consequences.”

Mr Trump’s threat is therefore best seen as performance – high-stakes, reckless performance, but performance all the same.

Other motives may be at play. In the coming days, the US president will have to unveil how he intends to counter Russia’s continuing aggression in Ukraine, underscored on Friday after an attack on Kyiv killed 31 people.

Secondary sanctions on countries buying Russian energy – chiefly China, India, Turkey and the United Arab Emirates – pose a major diplomatic headache.

Should Mr Trump choose to retreat on these threats, he can point to the submarine deployment as proof he is serious about Russia – a strategy whose stakes are higher but costs potentially much lower than escalating tariffs on allies Washington needs for goodwill in other arenas.

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