The death of Wagner boss Yevgeny Prigozhin and Vladimir Putin’s enigmatic comments about him highlights the rivalry, bitterness and strife at Russia’s summit. Yet it seems rash to interpret it as heralding radical change. Putin’s calamitous war seems bound to go on.

Ukraine’s summer offensive has inflicted substantial damage and losses upon Russian forces, especially by harrowing their rear areas, reserves and logistics hubs with long-range weapons. It will not, however, achieve its principal objectives, above all reaching the southeastern city of Melitopol, a key Russian communications link. This poses domestic morale difficulties for Volodymyr Zelensky in Kyiv, and more serious ones for his Western supporters.

The offensive was wildly oversold by hawks in the United States and Europe, who told governments that if they provided Ukraine with billions of dollars of advanced weapons, its army was capable of delivering a decisive victory. I was never among those who believed this — because none of my informed military friends on either side of the Atlantic did so.

They have argued since last winter that the Russians have created deep defences — above all, minefields — that the Ukrainians could not hope to break through. Moreover, Ukraine’s commanders, for all their courage and ingenuity, lack skills for conducting big all-arms battles. Based on reading and hearing such views from soldiers, I suggest that no matter what weapons the West supplies, Ukraine has no realistic prospect of winning back Crimea or the Eastern Donbas through military action.

Such remarks cause me and like-minded commentators to be denounced by zealots as an appeaser. They say: “How can we allow Russian aggression to succeed? We owe it to the incredibly brave Ukrainians to back them to the hilt.”

I agree. It is a vital generational interest to prevent the Russians from securing victory through their monstrous conduct. Americans and Europeans alike must keep reminding each other that the invasion of Ukraine and everything that has followed it — the atrocities, rapes, child kidnappings and terror bombings of civilians — are crimes against humanity.

But that does not mean we should embrace wishful thinking and fantasy strategy about the limits of the possible. This is especially true of those who preach a doctrine of “don’t give a yard!” while occupying comfortable armchairs at home. During Britain’s 1899-1902 Boer War against South Africa’s Afrikaner republics led by Paul Kruger, the poet Rudyard Kipling penned a contemptuous line about jingos in London who were “killing Kruger with your mouth”. In the West today, there is too much “killing Putin with your mouth”, not enough hard thinking.

None of the above should suggest a willingness to yield to Russia or to encourage Ukraine to do so. On the contrary, the historical challenge is to sustain the will of the West, and above all of the US, to continue providing billions of dollars and euros in cash and military aid, and to sustain Ukraine through what now seems destined to be an ordeal protracted over years. There cannot be peace until it is apparent to both sides that neither can prevail on the battlefield.

Putin has gambled that he and his people have more patience, staying power and guts than does the decadent West. We must prove him wrong. If we fail to do so — if we betray Ukraine — not only Putin but tyrants everywhere will conclude that aggression pays. They will repeat what Russia has done in Ukraine again and again and again, not only through our lives but through our children’s.

We must not succumb to gloom merely because this summer’s Ukrainian offensive does not achieve a decisive outcome. The great lesson of modern wars between powerful industrial states is that a ghastly amount of dying and killing has to happen before one side or the other prevails. There is seldom, if ever, a battlefield quick fix.

Some Westerners persuaded themselves after the Second World War that better generals and economic superiority over Germany had made it possible to achieve Allied victory at a fraction of the cost in human sacrifice that the First World War imposed on Britain and France. In truth, of course, attritional battles far bloodier than those of 1914-1918 took place between 1941 and 1945, but they were on the Eastern Front. The Russians spared Britain and the US from most of the human cost that had to be incurred by someone to smash the Nazi war machine.

Over the past 18 months, some optimistic assessments have been made about the weakness of Russia. We have been told by supposedly authoritative commentators that sanctions would bring the Kremlin to its knees; that the Russian people do not support Putin’s war; that the Russian army is about to collapse; that if the Ukrainians were given advanced fighter jets and Leopard tanks, they would go through the Russian defences like a knife goes through butter.

It was all nonsense, of course. Sanctions are hurting Russia, but because so many of its people are employees of the state, Putin can shield them from a fall in living standards. Russia has committed relatively fewer troops to this conflict, proportionate to its 140 million population, than did France to its doomed 1950s wars to preserve its overseas colonies.

On the credit side, even though Ukraine’s recent drone attacks inside Russia have inflicted little material damage, they are useful in bringing home to Putin’s people the reality that they are engaged in a struggle with an enemy capable of hitting back — and of exposing the emptiness of their president’s claims to be a successful steward of his nation’s security.

Putin has enjoyed dismaying success, however, in convincing Russians that they are engaged in an existential struggle against Western aggression. Recent new waves of military conscription have not provoked the sort of mass exits from the country seen last year.

Whatever claims to inside knowledge some Kremlin-watchers profess, no one, including Western intelligence, knows what goes on in Russia’s innermost circle of power. This was emphasised by the crazily optimistic forecasts made in July after the brief revolt by Wagner capo Yevgeny Prigozhin.

The undoubted tensions between the Kremlin and Russian military chiefs may yet precipitate a serious internal upheaval, although Prigozhin’s death emphasises the likely fate of any challenger to Putin. It is possible, though not probable, that Putin will fall. It is almost inevitable, however, that should this happen, he will be replaced by someone equally unpleasant and likewise committed to the war.

American Russia-watchers Andrea Kendall-Taylor and Erica Frantz observe justly about a successor to Putin in the latest issue of Foreign Affairs: “The track record of political transitions that follow the exits of longtime authoritarian leaders offers little room for optimism. The path to a better Russia is not just narrow — it is treacherous.”

If Russia was seen to suffer absolute defeat in Ukraine, Putin would likely be deposed. Since this remains implausible, however, Western governments will be wise to bet on Russia sustaining its hostility to their democracies while being led by Putin or someone like him.

Russians have always taken pride in their capacity to endure pain, and this national characteristic remains evident in the context of the Ukraine war. A Nordic general recently drew my attention to a Finnish saying: “You can fry a Russian in butter, but he is still a Russian.”

The West should make plain its willingness to indefinitely continue to arm and finance Ukraine — and ensure that it means what it says. Kipling’s poem cited above, urging British people to sustain their resolve in 1899, concluded: “Pass the hat for your credit’s sake / and pay-pay-pay!” Only if and when the Russians believe that we will do this, and see no prospect of their forces prevailing on the battlefield, can there be talks.

It is a fantasy as pernicious as those of the Western hawks who preach absolute Ukrainian victory to suppose that there can be any early compromise settlement with Moscow. Today, Putin remains committed to achieving hegemony over Ukraine.

Western nations are still shamefully indulgent to Russian oligarchs and their families holding huge possessions in Europe and disporting themselves on beaches and ski slopes. I was shocked last year, after a holiday at a famous Italian lake hotel, to discover that it remains the property of one of Putin’s closest associates — the proceeds from our bill payments went almost directly to the Kremlin.

Until we tighten the screws on such people, there is little hope that they will see any incentive to withdraw support from Russia’s president. It should not be hard to do this if — a big if — the will to do so exists within Western governments, most of which are deplorably reluctant to expel or freeze Russian billions in their banks.

Meanwhile, as Fiona Hill, a former official at the US National Security Council and now a senior fellow at Brookings, said in an important lecture earlier this year: “We need a diplomatic surge — a skilful and patient effort alongside the vital military track … We must push back against Putin’s disinformation and anti-US and Nato narratives.”

Hill emphasised how much of the world is scarily willing to accept Russian propaganda about Ukraine as a puppet of Nato, and Nato likewise of the US. If Western arms factories need to tool up to support a long war on Ukrainian battlefields, Washington and its allies need to tool up for a protracted teach-in to make neutral or Moscow-leaning nations see why Putin’s aggression is bad for everyone.

At the peak of Russia’s invasion in spring 2022, its forces controlled 140,000 square kilometres of Ukrainian territory. Today, this has shrunk to 109,000 square kilometres. This still amounts, however, to one sixth of pre-2014 Ukraine.

François Heisbourg, former president of the International Institute of Strategic Studies, is the author of a new book on lessons from this war. He argues first, of course, for continuing to arm President Zelensky’s nation to strengthen its battlefield position, because only when this is achieved might Moscow join a meaningful negotiation.

Thereafter, he draws an interesting comparison with West Germany in the 1950s. Chancellor Konrad Adenauer never formally acknowledged communist East Germany as a separate state, but nonetheless relinquished reunification as a commitment of his government. Adenauer, with essential American backing, presided over West German rearmament as a central pillar of the Nato defence of Western Europe against the Warsaw Pact. The Soviet Union bitterly opposed this but was obliged to acquiesce.

Heisbourg writes scornfully of modern Germany’s insistence that Ukraine must not join Nato as long as its borders are in dispute, which he suggests is ironic against the background of late 20th-century German history. It seems obvious that Ukraine cannot accept any sort of ceasefire without ironclad security guarantees, which probably means membership of Nato. Without such protection, Russia would be free to renew its aggression at will, an intolerable prospect.

But Heisbourg thus raises a possibility that when this war has run its bloody course for some time longer, a ceasefire may take place that does not recognise Russian occupation of Ukrainian territory, but imposes upon Moscow the penalty for its actions, by obliging it to acquiesce in Ukrainian Nato membership. This week, some Nato officials in Europe have been hinting at such a possible outcome.

The war is certain to continue past 2024 because Putin is pinning so many hopes upon a Trump electoral victory in the US, followed by Republican withdrawal of support from Ukraine. Only when that huge uncertainty is resolved is there any possibility of a halt to the killing. Meanwhile, all of us fortunate to inhabit democracies that are unthreatened by violent external aggression should recognise that Ukraine’s fight is the fight of us all. This will remain so, whatever the outcome of this summer’s battles. Prigozhin’s reported death justifies a brief spasm of joy in Kyiv because the world is rid of a murderous brute. But Putin, alas, has many more such men where the Wagner boss came from.

War cannot be ended like a baseball game — to suit the convenience of an impatient throng of spectators wanting their dinners. As Ukrainian foreign minister Dmytro Kuleba said last week, responding to sceptical questioning about his country’s offensive: “It’s easy to say that you want everything faster when you are not there.”

• Max Hastings is a Bloomberg Opinion columnist