The North Korean army is estimated to have over one million soldiers, giving Putin a potentially large pool of reserves to replenish his forces. Russia is estimated to be losing more than 1,000 men per day using mass infantry tactics.

Ukraine, by contrast, has been finding it tough to replenish its front lines. Recruitment has dropped – despite increased press-gang powers – because men see a front-line posting as a one-way ticket to death or serious injury.

And this, said John Foreman, Britain’s former defence attaché in Moscow, made the North Korean troop deployment an important part of the Kremlin’s calculation for winning the war.

“It means tapping a new source of cannon fodder,” he said. “It also means using non-Russians. No one will care if the North Korean troops are killed.”

North Korean soldiers have not been seen in battle since the Cold War when they were deployed in various fringe wars as Soviet allies and proxies.

According to reports by Russian military bloggers, at least 18 North Korean soldiers have already deserted their training camps in Russia.

The US has said that it is “concerned” about the reports that North Korea may soon be joining Russia’s war against Ukraine.