On 9 May, Russians celebrate the 70th anniversary of victory over Nazi Germany in 1945. The leaders of the Soviet Union's allies in that conflict, Great Britain and the US, will not be present. Chinese President Xi Jinping will attend. But of major Western leaders only German Chancellor Angela Merkel will go, not to the parade but to a subsequent wreath-laying ceremony in honour of the Soviet war dead.

This is a far cry from a decade ago. United by the War on Terror, US President George W Bush and other Western leaders stood alongside Russian President Vladimir Putin at the 2005 parade in Red Square. 

Since then, much-read works like Timothy Snyder's Bloodlands and Anne Applebaum's Gulag and Iron Curtain have asserted or implied the equivalence of Stalin's Soviet Union and Hitler's Germany. This revival of a Cold War thesis of interchangeable Nazi/Soviet totalitarianisms makes it an open question whether these Western leaders would have made the journey to Moscow even without the conflict in Ukraine. 

Perhaps no historical event is as familiar as the Second World War. But 'Russia's War', as Richard Overy called it in his landmark 1997 work, reminds us how strange and terrible it really was.

In the first six months of the German invasion (June to December 1941), 2.6 million Soviet soldiers were killed in battle and 3.35 million taken prisoner. Herded into open pens, most of them perished. Some 7 million Soviet citizens were deported to Germany as slaves, the majority from Soviet Ukraine.

Those left behind endured trials without comparison outside Japanese-occupied China. By January 1942, 4000-5000 besieged Leningraders were dying a day. The toll would reach one million. People ate glue boiled off the wallpaper, and the flesh of corpses. Elsewhere, a 66-hour week with one day off per month earned workers 1300 to 1900 calories a day. Half a million Soviet citizens died as victims of German air raids – ten times more than in the Blitz on British cities and around the same number of German civilians killed in Anglo-American bombing of the Reich. 

Total Soviet military deaths ran to 9 million. War is by nature awful, but the Eastern Front was hellish. The Battles of Moscow and Stalingrad, which each claimed about half a million Soviet soldiers, were fought in temperatures of around minus 30 degrees celsius: Soviet soldiers following retreating Nazis found whole units frozen solid, their legs sawn off by survivors to retrieve their boots. The Soviet secret police, the NKVD, executed 13,500 alleged deserters. When British and American troops landed in Normandy, 58 German divisions were in Western Europe, 15 near the front. In the east in 1944, the Red Army faced 228.

The death of 25 million civilians defies comprehension – and yet was less than the number Hitler had hoped to starve in the first year. By comparison, Allied dead in almost three years of fighting in North Africa amounted to 250,000. In Europe and the Pacific, the British suffered around half a million fatalities, soldiers and civilians; the Americans slightly less. Australia lost 41,200. 

Yet by 1942 Soviet arms production outstripped Germany's, building 1.5 times as many aircraft, 2.5 times as many tanks and over four times as many artillery guns – the output of 2500 factories dismantled in the face of the German invasion, carried east on trains and reassembled in the relative safety of the Urals and Siberia. The workforce sometimes lived in holes dug out of the earth. Lend-Lease contributed army jeeps, telephone wire and food. Soviet soldiers called tins of American Spam 'Second Fronts'. 

At the top stood Stalin, whose mistakes cost the lives of thousands in under-prepared defences and vain offensives. He wrung obedience from his people through a ruthless combination of mass murder and torture, but ultimately proved a far more effective warlord than Hitler and a better politician than Roosevelt, Truman or Churchill. 

In its scale of suffering, the Russians seem often to have been fighting a completely different war from that of the British and the Americans. Yet 'our' war, too, depended on its outcome. Without Russia's war, we not only underestimate the horror of the Nazis; we fail to appreciate the strictly limited nature of Western victory.

Of the 5.2 million German soldiers killed in the war, the Red Army killed 4.7 million. Sir Max Hastings writes in his All Hell Let Loose: 'There is a powerful argument that only a warlord as bereft of scruple or compassion as Stalin, presiding over a society in which ruthlessness was even more institutionalized than in Germany, could have destroyed Nazism.' In his Second World War, Antony Beevor similarly remarks that 'the great hardships of life in the Soviet Union had toughened all those that served in the Red Army. The armies of western democracies could not be expected to withstand the same level of hardship.'

But if the War, as it was fought, was unwinnable by liberal democracies, the unspoken message of Western leaders' decision to absent themselves from next week's Victory Day celebrations is that Russia's war is superfluous to requirements – too hard to reconcile to our narrative of a war for freedom. In Gulag, Applebaum writes:

We remember D-Day, the liberation of the Nazi concentration camps, the children welcoming American GIs with cheers on the streets. No one wants to be told that there was another, darker side to Allied victory, or that the camps of Stalin, our ally, expanded just as the camps of Hitler, our enemy were liberated. 

The combined effect, she writes, is to 'undermine the moral clarity of our memories of that era'. But what is it to seek 'moral clarity' where only the relative immorality of power is to be found? 

British and American governments found a Soviet Eastern Europe preferable in 1945 to a Nazi one in 1939. Once he had the atom bomb, Stalin refrained from using it. Is it possible to imagine Cold War deterrence with the Nazis? That Putin has been compared in the West to both Hitler and Stalin points to the confusion.

In other ways, the Second World War still haunts Eastern Europe. Pro-Russian rebels proclaim 'People's Republics' under the hammer and sickle in the Donbas; Ukrainian paramilitaries brandish insignia reminiscent of the Nazi SS. Asserting the equivalence between Stalin's and Hitler's regimes is forbidden in Russia – and enshrined, since last month, as law in Ukraine.

As Igor Okunev, vice-dean of the Moscow Institute for International Relations, wrote in an essay last year, the conflict in Ukraine is also a war about a contested past: 

Some analysts explain the developments in Ukraine by ethnic hatred: Russians are protecting ethnic Russians living in Ukraine from Ukrainians. But it is not an ethnic, religious or some social split that is plaguing Ukraine, it is the attitude towards the past which causes the confrontation between the 'Soviets' and the 'Banderovites,' the followers of Ukraine's nationalist leader Stepan Bandera.

When I asked Okunev by email what the war means to ordinary Russians, he replied: 

In the history of Russia's very controversial twentieth century, victory in WWII is probably the only event that consolidates the whole society. It is both very patriotic and still very individual day. […] Every Russian family lost someone in this war. In the Western world, the age we live in begins with the fall of the Soviet Union. In Russia, it starts with Victory Day [in 1945]. It is an event that determines our vision of the world. Russia is not a loser in Cold War but a victor in WWII.

I then asked his view on the equivalence between Hitler's Germany and Stalin's USSR. His reply would find few takers in the West today:

Both Hitler and Stalin led totalitarian regimes, but you can't put them on the same level. Hitler's goal was to kill Eastern Europe while Stalin wanted to give it Communism. You can dislike both goals but they are not equal. In this sense, the Soviet Army saved Eastern Europe from death.

This gulf in historical understanding between Russia and the West neatly reflects their political differences and may partly explain them. So long as Russia refuses to repudiate its Stalinist past as Germany repudiated the Nazis, the totalitarian threat to liberal democracy hasn't gone away. To Snyder and other liberals, it has reared its head again in Putin's Russia. On the other hand, if, as the realists have it, the conflict in Ukraine flows from the West's unwarranted dismissal of the realities of power in Eastern Europe, taking at face-value the historiographical sea-change in the meaning of Russia's war should be numbered among the 'liberal delusions' to blame. 

Even if we don't go that far, Russia's Second World War remains an antidote to the cloying sentimentality of our own commemorative rituals that simplistically equate virtue and victory, sacrifice and freedom. 

'No one doubts that victory could have been bought at a lower price', writes Overy, 'with less oppression and more humanity, without the countless dead. But that was the tragedy of the Soviet war. The sacrifices of a tormented people brought victory but not emancipation, a moment of bitter-sweet triumph in a long history of loss.'

Russia's war is troubling, as war should be. 

Some will argue that celebrating the Soviet contribution to victory in 1945 endorses a lamentable tradition of Russian conservatism that from Ivan the Terrible and Peter the Great to Putin has sacrificed the individual to the state. That's what makes the flowers that Merkel will lay on the Tomb of the Unknown Soldier so poignant. In 2013, Germany's head-in-the-sand diplomacy helped make the present crisis possible. But Berlin has since led efforts to resolve it. This time, I think the German chancellor has got it right.

Photo courtesy of Flickr user russianfront1941.