It is worth asking if Nato is being too timid by refusing to give arms to Ukraine

Even making generous allowances for propaganda, Ukrainian defence forces do seem to have been able to hold back – and occasionally push back – the Russian invaders.

Russia has certainly made gains on all sides, though at considerable cost in human suffering, but the war is not going according to any of the plans that have been implemented over the past month. By now, Vladimir Putin must have thought he’d be taking the salute at the victorious military parade in Red Square, with Ukraine dismembered and some docile mini-Putin dictator installed in Kyiv. It has not turned out that way.

To borrow a famous coinage of George W Bush, President Putin seems to have misunderestimated Volodymyr Zelensky and the people of Ukraine. The bombings of cities can continue indefinitely, but they do not, and will not, amount to any meaningful victory for Russia.

Now, President Zelensky has appealed to the Nato leaders meeting in Brussels to send him 500 tanks – to give him the tools to finish the job, as another wartime statesman put it. Ukraine is offering to buy them. The leaders in question must be severely tempted by the idea of seeing Russia defeated for the sake of such a modest contribution to Ukraine’s war effort, and there is nothing in the Atlantic Charter that would prevent them from making it.

But there are obstacles in the form of policy and doctrine, because Nato insists on supplying only “defensive” equipment. That was why the gift of elderly MiG jets from Poland to Ukraine was blocked, and why the tanks will be similarly refused.

It is at least worth asking whether Nato is being too timid here. The supply of tanks, or jets for that matter, would not bring Nato troops or pilots into conflict with Russians. Ukraine is free to buy weapons of war wherever it wishes, just as Russia is now rumoured to be sourcing drones from China and soldiers from Syria.

It is not immediately clear why helping Ukraine by sending old aircraft is thought to be an act of war while supplying state-of-the-art surface-to-air missiles (which will do the same job) is thought entirely legitimate. One is classified as offensive and the other defensive kit, but to a Russian air force fighter-bomber there is no practical difference.

It is striking, too, that despite dark threats about “legitimate targets”, Russia hasn’t made a serious effort to halt the flow of missiles and other aid moving into Ukraine from the west. It feels as though the Russians won’t push their luck as far as the Polish border.

Though Nato is more unified and effective than seemed possible in the days when Donald Trump threatened to pull out of the alliance and Germany was still trying to find a way to trust Mr Putin, it is still cowed by Moscow. There is no sign that the alliance is prepared to call Mr Putin’s bluff, or set down any “red lines” about this war.

Instead, Nato will redouble its supplies of defensive kit, and, crucially, materials to deal with the use of chemical, biological or even battlefield nuclear weapons – a fresh horror that now looks increasingly likely.

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The word “genocide” is overused, but the uncomfortable fact is that, even if Mr Putin freely declared that such was the aim of his war, Nato would still not intervene beyond its present support. The Russian president correctly surmises that Nato will not react to any number of war crimes, and presses on with his campaign.

If Russia were deterred as easily by Nato as Nato is terrified by Russia, this war would be over by now, and probably wouldn’t have started. The last few weeks have shown what a formidable ally Ukraine could be.

Lessons do seem to have been learnt, to the extent that vast military resources are being devoted to Nato’s eastern flank. There is more pressure on the likes of Germany to radically scale back their use of Russian oil and gas (assuming Mr Putin doesn’t cut them off anyway).

Militarily, the Baltic republics are especially vulnerable, with the Russian exclave of Kaliningrad complicating the scene, and in due course we may expect Mr Putin to probe Russia’s borderlands with Nato members in eastern European non-Nato states such as Moldova and Finland.

At the moment, though, he is badly bogged down in Ukraine, and probably does not wish to open up new fronts. In short, we find ourselves in a perverse situation, in which Ukraine is effectively fighting to protect Nato member states such as Latvia from the Russian threat, but Nato is not returning the favour. It is shameful, but – worse than that – it is a strategic error.