Jonathan Romney on In the Fog: The walking dead lost in no man's land

This sombre, minimalist study of the spiritual vacuum of war – in which few shots are actually fired – is a masterly work of true depth

You may not have heard of Sergei Loznitsa, but he's one hell of a film-maker. UK distributors missed a trick in not giving a cinema release to the former documentarist's first fiction feature My Joy (2010). Ostensibly about a lorry driver who takes a wrong turn and is violently sucked into the darkness of the Russian backwoods, this episodic bad trip was a sort of post- Soviet Deliverance, with rot-gut vodka instead of moonshine. It suggested arbitrary violence and catastrophe are, and have always been, part of Russian life – which explains why Loznitsa, who grew up in Ukraine, seems to be not terribly popular in Russian film circles.

His follow-up In the Fog is more classical, but no less daring – and would have made just as worthy a Palme d'Or as Michael Haneke's Amour in Cannes last year. In the Fog is a somewhat minimalist war story – few shots are fired. But it powerfully conveys a sense of war as a constant force determining the turns of misfortune for innocent and compromised alike. In war, it suggests, you can never go home again.

The time is 1942 in a region of what is Belorus today, then under German occupation. The film opens with an extended single shot that starts by following prisoners under German guard; as they move out of sight, we see villagers looking on, while in the background we hear an announcement warning them not to support the local partisans. Finally we hear, but don't see, a hanging. Instead of showing us dangling corpses, Loznitsa's camera comes to rest on the sight of a sheep grazing – right next to a wagon piled with sheep's bones.

We next meet a man named Sushenya (Vladimir Svirskiy) spending a quiet evening at home when two men arrive at his door. It's clear that they've come to lead him to his execution, and Sushenya, with what seems misguided (or saintly) fatalism, knows that he has no choice but to go. He is one of four railway workers arrested by the Germans, and the only one spared hanging; naturally, he's suspected of betraying them.

So Susheyna sets off with Burov (Vlad Abashin) and Voitik (Sergei Kolesov) into a pine forest. When one of Sushenya's captors is wounded, the condemned man finds himself tending to his would-be killer, carrying him on his back through the trees. All this – his docile acceptance, his compassion towards his aggressor – seems the sort of behaviour you would only ever find in a Russian war film. But Loznitsa's calm narrative authority is such that you accept In the Fog both as a plausible wartime anecdote and as a philosophical parable about what's left of the human spirit when war strips off its civilised carapace.

Based on a novel by Vasil Bykov, In the Fog develops a simple but complex structure. Pausing in the forest, it flashes back to Burov's past, showing his revenge on collaborationist police; now this seemingly loveless warrior reveals his own vulnerable humanity. We also see the contrasting history of the rather less admirable Voitik.

And we learn what led Susheyna to this desperate pass: his supposed involvement in an act of sabotage. Here, there's a chilling cameo by the Romanian actor Vlad Ivanov (the creepy abortionist in 4 Months, 3 Weeks & 2 Days) as the German commandant who does the cruellest thing of all – freeing Sushenya while his comrades die. This makes him a pariah, a walking dead man – for war, the film suggests, makes walking dead out of all who experience it.

Loznitsa's film belongs to that increasingly familiar cinematic sub-genre of stories about interlocking fates – e.g. Crash, Babel. But in its concision and philosophical lucidity, In the Fog is in a field of its own. At its heart is Vladimir Svirskiy's Sushenya, whose shaggy beard and sad, candid features make him look uncannily like the peasants of 19th-century Russian paintings – and sometimes like a Christ figure. He's a magnetic centre to the action, especially when he turns a calm gaze straight to camera, silently asking us how we'd acquit ourselves in infernal circumstances. Vlad Abashin is superb too, his heavy monotone suggests a man emptied out by the burden of his grim duty.

Modern Russian cinema has a fearsome reputation in depicting war – most spectacularly in Elem Klimov's monumentally grim Come and See (1985). But Loznitsa's film is less about the materiality of war than about the idea of it, and its effect on society and the soul. This is a film of real depth and substance, its anecdotal perfection echoing not only the Russian war stories of Isaac Babel, but also such masters as Maupassant and Graham Greene. Shot in long, measured takes and claustrophobic widescreen by Romanian cameraman Oleg Mutu, this is an imposingly sombre piece, but also a compelling, nerve-racking narrative – and one of the year's unmissables.