Nato military assistance thus far – even the short-range anti-tank missiles delivered by the UK this week – does not seriously challenge Russia’s military dominance. But the Kremlin fears it could erode its leverage if left unchecked.

Even worse, from Vladimir Putin’s point of view, would be if Ukraine’s domestic defence industry developed long-range missiles able to reach far into Russia, giving it a deterrent against his own feared Iskanders.

Viewed from the Kremlin, the costs of fighting are now dwarfed by the risks of inaction, argues Rob Lee, a fellow in the Foreign Policy Research Institute’s Eurasia Program who has followed the Russian military build-up closely.

You do not have to look far for confirmation that the ruling elite in Moscow grasp just how dangerous Mr Putin’s current course is.

‘Russia does not want war’

Sergei Karaganov, a Russian academic considered to speak for the conservative and hawkish wing of the country’s military and foreign policy establishment, said this week that Russia does not want to fight a war for Ukraine.

But he argued that a re-run of the 1963 Cuban Missile Crisis, which brought the world to the brink of nuclear destruction, might be the only way to control what he called the “cancer” of Nato expansion.

“Many of us seem to have come to the conclusion that if something similar doesn’t happen now, if our partners do not sober up, things will definitely end up in a hot war,” he said in an interview with Argumenti i Fakti, a Russian newspaper.

“Russia wants to prevent that. We cannot allow a repeat of the 22 June 1941 in some new form,” he said, referring to the day Nazi Germany invaded the Soviet Union.

To Western ears, such comparisons are as paranoid as they are insulting.

But that does not make the danger any less real.