Russian leader Vladimir Putin sent nuclear submarines into the North Atlantic one day after his chilling threat to the West, it has been reported.
Not long after the invasion of Ukraine, Putin ordered his nuclear deterrent forces on alert he sent several Russian submarines capable of carrying 16 ballistic missiles each sailed into the North Atlantic, it has emerged.
At the time, nuclear experts told The Mirror that this was "posturing" rather than a real nuclear threat.
It has now been reported they returned to Russia shortly afterwards, however western intelligence is now keeping a closer eye on Putin's nuclear arsenal.
Putin has the largest stockpile of nuclear warheads in the world with 4,447 - thousands are thought to be classed as tactical - meaning they are intended to eliminate enemy targets in a specific area without causing widespread destruction.
A navy source told The Times: "The majority of Russian conventional weapons can be retrofitted with a low-yield nuclear capability.
"It is more complex than ‘plug and play’ but the Russians are quite innovative in what they put in front of bombs and missiles."
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Putin's justification for invading Ukraine was to "de-Nazify" the country, not destroy it as experts say they don't see evidence that the Kremlin is gearing up to launch nuclear weapons.
A western official said that there had been no sign in the conflict so far of any nuclear warheads being loaded onto missiles bound for Ukraine.
At the time Putin put his nuclear forces on special alert, Dr Matthew Kroenig, Director of the Scowcroft Strategy Initiative at the Atlantic Council, told The Mirror Online there were two reasons to move his weapons.
He said it so Putin would be less vulnerable to a nuclear attack with the weapons being in one place and to move them into strategic places where they can be launched from.
He said: "This is part of Russian strategy. I don't think we are getting ready for a nuclear war.
"It's like in the animal kingdom when animals make themselves look really big before a fight.
"What Putin is trying to do is intimidate us to say 'stay out of Ukraine'".
Dr Kroenig said that Putin used a similar strategy in 2014 during the annexation of Crimea.
He added: "This development does make things more dangerous with nukes moving around, but Russia did this in 2014 and they use nuclear deterrence as an offensive strategy."
