When Philip Oppenheimer, father of the atomic bomb, made his famous observation after testing a thermonuclear weapon: ‘I am become death, destroyer of worlds’, he didn’t come out with it in a spirit of smug celebration.

Vladimir Putin, by contrast, takes perverse delight in advertising his appetite for destruction. He looked delighted this week with an apparently successful test of his new ‘Satan II’ missile (nice rocket, nice name). Satan II is a tasty bit of kit, which if it works as intended will haul a dozen nuclear warheads into space, then drop them at hypersonic speeds on a dozen separate targets. Each of the warheads is about forty times more powerful than the Hiroshima and Nagasaki bombs, and one missile could devastate an area of quarter of a million square miles: enough to destroy in one go almost all the property owned by Ed Sheeran.

Setting aside the desirability of this outcome, Putin must hope that his bit of nuclear theatre ramps up the credibility of his metronomic threats of a holocaust meeting any country bold enough to come to the rescue of Ukraine.

No-one should doubt that Putin, like the USA and China, has the capacity to destroy the planet if he so desires. Equally, no-one should be bluffed into thinking that he will. Unlike NATO military doctrine, all-out nuclear war is a conflict Putin knows he can’t win. He wants a renewed Russian empire to rule, not a charred wasteland. Even if tittle-tattle that Putin is gravely ill is correct, he is fighting his ‘special military operation’ in Ukraine for his legacy; to be remembered, in his lifetime or after it, as the man who reunited the Russia of the Tsars. He wants to be remembered in this capacity by something other than cockroaches and, knowing the man’s uncanny capacity for survival, Boris Johnson.

Nuclear bullshit is central to Russian strategy in Ukraine. It has worked beautifully in keeping NATO at bay. Putin’s fans and enablers the world over have been pleased to parrot his threats. But Vladimir Putin enjoys luxury and wealth. He has made himself, on a modest salary, one of the richest men in the world. He has built a great palace by the Black Sea. There is little point in building up empires and palaces to see them all reduced to dust. So the reasonable assumption is that all his big talk about nuclear war is bluff.

Military doctrine is of course right that assumption is the mother of all foul-ups (not the actual ‘f’ word used at Sandhurst) but some assumptions are safer than others. Letting Putin scare the West out of a military response to Russian barbarism in Ukraine has been a great strategic mistake.

It’s not NATO’s worst mistake in handling Russia. Telling Putin explicitly that an invasion would meet no military response (rather than leaving creative ambiguity around the likelihood of armed intervention) was staggeringly naïve. When tanks started rolling, the best time for NATO and the EU to react with military force was the second they crossed Ukraine’s border. A display of overwhelming air power in Ukraine’s defence –followed by a short truce to allow Putin to assess the wisdom of his campaign– might have stopped the invasion in its tracks. Instead, we sat back and deplored it all from a distance.

What about the prospect of Russia detonating a tactical nuclear weapon? It’s a risk the West should run. It wouldn’t start a nuclear war, or carry the risk of repercussions (as Biden bizarrely put it with reference to the possibility of a Russian chemical attack) ‘in kind’. What it would do is bring down on Russia an overwhelming conventional response. We have now had two months to gauge the ability of the Russian military to respond to this, and if they can’t respond adequately to Ukrainian tractors, you can bet they wouldn’t do too well in the face of an all-out NATO assault.

This makes NATO’s position stronger than it was during the missed opportunities of the first stage of the war.

Putin’s campaign is entering a phase in which Russia may achieve some results. The purported justification for invading Ukraine was to save ethnic Russians in Donetsk and Luhansk from awful Ukrainian Nazis; Russia now seems set to achieve this by laying waste to all the regions’ centres of population; for which liberation their remaining inhabitants are expected to be perpetually grateful to Mother Russia.

Putin could very probably have annexed these regions back in late February without meeting much in the way of Ukrainian defence or Western sanctions, and Russian troops –as in Crimea– would have been met at worst with light resistance, at best with some degree of enthusiasm. Joe Biden had already told Russia, whether he meant to or not, that a ‘limited incursion’ wouldn’t be that big a deal.

It is plausible that the successful annexation of these areas will be achieved in time for the victory day celebrations on May 9, which might in turn give Putin the opportunity to take a breather and reassess the viability of his wider campaign. Conquering all of Ukraine proved impossible first time round, and he must be persuaded that it will remain impossible at any point in the future. Russia has lost a mind-boggling number of men and materiel. Re-arming Ukraine to make similar losses a certainty in any future assault is now NATO’s greatest priority.

Satan II isn’t ready to blow us all to hell yet and won’t be for a while. Even if NATO can’t find the will to send troops to beat Russia out of Donbas, the time to send heavy weapons –tanks, artillery and aircraft– to Ukraine is now.