If Ukraine lasts for another thousand years, people will still say, ‘This was their finest hour.’ The Ukrainians’ magnificent defiance will shape their country’s image in the world for generations to come, as the lone stand led by Winston Churchill did for Britain. But what almost certainly awaits Ukrainians in the next few days is far worse than what the British went through in 1940. They are about to face a Russian campaign of long-distance bombardment and siege to try to break their will to resist, through fear, hunger, thirst, cold, sickness and all the other consequences of indiscriminate destruction. Mariupol has already been devastated. Now the Chechen butcher Ramzan Kadyrov has announced he is in Ukraine, knife sharpened for more butchery. Ukrainian mayors of capital cities have been abducted and western intelligence agencies report Russian plans for public executions. In a word: terror.

‘We will never surrender,’ said Daniel Bilak, a lawyer turned home army defender of Kiev, in a video discussion I participated in a few days ago. Another Churchillian echo. Later on, as Russian forces close in on the Ukrainian capital, he emails me to express his hope that he will make it ‘beyond tomorrow’. He adds an emoji, but there is no emoji adequate for that thought.

Discussion of the war in Ukraine far too quickly slides off onto other subjects – what if Putin attacks Nato? What about China? What does this mean for our economy and the future of world order? All very important issues, of course, but don’t let them distract us from the most urgent question: what can we do to help Ukrainians defend their country, their freedom and their democracy?

President Volodymyr Zelensky gives a clear answer in the tweets he sends following every conversation with a European leader. (If you don’t already follow him on Twitter, please do. His Twitter feed is a masterclass in 21st-century war leadership.) Again and again, the Churchill of Ukraine comes back to three things: more military support, more sanctions and a better future for Ukraine in Europe. On all three, we can do more.

The scale of western arms supplies has been formidable. Leading the way, the United States has given more than $2 billion worth of defence aid. Britain can be proud of having seen the need earlier than most European countries, training upwards of 20,000 Ukrainian soldiers and sending in more than 3,600 light, effective anti-tank missiles. Now almost the entire EU has joined in, including Germany. As the missile attack on 14 March on a weapons transit base in western Ukraine showed, Russian forces are beginning to close down the western supply lines. We still have a few more days, perhaps weeks, in which we should try to get in more weapons and ammunition, including sophisticated air defence weapons and basic supplies, including food, water and medicine, to help cities like Kiev withstand an almost medieval siege.

But Nato is not going to deliver the fighter planes or impose the no-fly zone that the Ukrainians keep asking for. It is not going to go to war with Russia. The Polish position on this has been fascinating. For as long as I can remember, Poles have been making me feel guilty about how little the West did to make good on the security guarantee Britain gave to defend Poland in 1939 and how we abandoned them to Stalin at Yalta in 1945. The argument was identical to that used by Zelensky today: you have abandoned us to fight alone in defence of freedom, Europe and the West. But now that Poland is itself safely part of the West, inside Nato and the EU, Poles start sounding more like the British in 1945. Huge sympathy and humanitarian solidarity, but we have to be responsible and think long term. We can’t risk another world war.

All the more reason then, to do more on the other two main fronts identified by Zelensky. The package of sanctions already agreed is unprecedented. The British government, so admirably quick in providing military support to Ukraine, has been shamefully slow in cracking down on dirty Russian money in London and opening our doors to Ukrainian refugees. In these respects, the EU was quicker. But the one big thing we can do to escalate sanctions pressure on Vladimir Putin still lies in continental Europe, not in Britain or the US. This is to stop oil and gas imports from Russia.

Among the many mistakes made after Putin’s seizure of Crimea in 2014, that turning point at which Europe failed to turn, one of the most serious was to continue and even increase energy dependence on Russia. Last year, 30 per cent of Germany’s primary energy supply came from Russian oil, gas and coal. That includes no less than 55 per cent of its gas. A recent careful study of the economic cost of stopping German energy imports from Russia estimates the negative impact would be between 1 per cent and 3 per cent of GDP or (in the worst case) around €1,000 per person.

You can understand the reluctance to include oil and gas in sanctions. But I’m beginning to think that even this may join the rapidly expanding abattoir of Germany’s slaughtered sacred cows. Germans have to weigh the economic cost of stopping energy imports from Russia against the moral cost of continuing to pay billions into Putin’s war chest, at a time when he is conducting a war of terror on the very soil where Nazi Germany conducted such a war 80 years ago. Such is the genuine popular outrage in Germany that this further step may yet be taken, perhaps starting with oil and proceeding to gas.

Zelensky’s third key demand is for Ukraine to be recognised as a candidate for EU membership. In the middle of a war, his own life threatened not just by bombs but by death squads, this European perspective is that important to him. The EU’s response at the Versailles summit on 10 March was extremely disappointing. With a load of waffle about ‘belonging to the European family’, Ukraine’s application was sent to the European Commission for review. Behind this is the hard fact that many EU leaders, including Emmanuel Macron, don’t actually want Ukraine to be a member of the EU – ever. I deplore this lack of vision. Yet even short of the prospect of membership, there is still much that Europe, including non-EU members such as Britain, can do – together with the United States and other western allies.

Postwar Ukraine will need a massive reconstruction plan, with billions of euros and dollars coming from the entire West. Let’s not call it a Marshall Plan – for the past half-century is strewn with the ghosts of Marshall Plans that were promised but never delivered. How about the ‘Zelensky Plan’? This would also create conditions in which the millions of Ukrainian refugees in central and western Europe will be able to return home.

Along this path, there are many helpful halfway houses of closer association. Ukrainians already have visa-free travel to the EU. In the long run, it might include membership of the European Economic Area. Ironically enough, coming from completely different directions, the United Kingdom and Ukraine – UK and UKR – might end up in some of the same larger circles of a wider Europe.

Here, the long-term vision loops back to immediate needs. I would love to believe in a Miracle on the Dnieper, in which Ukraine simply defeats Russia as Poland unexpectedly trounced the fledgling Soviet Union in the Miracle on the Vistula in 1920. But this really would require a miracle. Failing that, this terrible war will have to grind its way to the point described by the strategic thinker Lawrence Freedman as a ‘hurting stalemate’, when both sides recognise they have to negotiate a peace.

Our immediate goal must be to ensure Putin gets hurt as much as possible and the Ukrainians as little. But at that difficult moment, Zelensky will have to make some bitter concessions in return for the withdrawal of Russian troops. They will probably include neutrality – as the Ukrainian president already hinted on Tuesday, saying Ukraine will not be in Nato – and some sort of conditional or de facto acceptance of Putin’s totally illegitimate territorial seizures in Crimea and the Donetsk and Luhansk provinces. At the end of its heroic Winter War against the Soviet Union in 1939-40, Finland conceded about a tenth of its territory, but it remained a sovereign, independent, democratic country – albeit ‘Finlandised’.

Against such a loss, Zelensky badly needs some big win to show his people. The reconstruction plan and European perspective is that win. The more concrete, generous and far-reaching our offer can be, the more Ukrainians will feel that their sacrifice was not in vain. In all this, we must be guided by the Ukrainians. If they want us to lift some sanctions on Russia in response to a Russian withdrawal from Ukraine, we must do it. But it is also in our power to give Ukrainians the historical sense that, though they may have lost some battles, in the end they will, at huge cost, have won the war. The war for Ukraine’s freedom and its proper place in Europe.