PEOPLE WHO STILL have it in for the British Empire like to say it was run, at least on its fringes, by bigoted twits; the failed, dim and degenerate offspring of the landed gentry, whose more talented siblings found respectable perches in London or the shires and covered up for their ne'er-do-well brothers, or simply disowned them, when news of their misdeeds trickled back to the imperial metropole.

Perhaps. And the same is true to an extent of the French, the Belgians and the Dutch. But no Western European empire, surely, produced anyone quite like Freiherr Roman Nikolai Maximilian von Ungern-Sternberg. He was, as James Palmer admits 70 pages into this biography, an “upper-class loser”. Fortunately for readers, if not for Mongolia, he was more besides: a mad crusader in the name of tsarism, Buddhism and anti-Semitism, all mashed together by the unequalled violence of his era. He was a homicidal maniac who admitted killing women and children in his rampages across Siberia so as to “leave no tail”; and a mystic, a walking negation of the Enlightenment who seemed to recoil at the merest hint of reason or civilisation.

Palmer's subject is a man who styled himself heir to Genghis Khan, even though he was an ethnic German bound into the Russian empire by virtue of his family's estates in Estonia. Ungern was a loser, though not a nobody: in 1920 he briefly liberated much of Mongolia from Chinese hegemony, and for a longer period he inspired terror through much of Asia. He also smoked far too much opium and was known to ride into battle in yellow silk robes on a white mare.

An obvious subject for rollicking popular history, you might have thought - so why the 80-year wait? The main answer is a chronic scarcity of reliable sources, which Palmer acknowledges early on. His most substantial achievement here is to conjure a convincing portrait from the tangle of legend and snapshots (including a few actual early photographs) that Ungern left behind. Another answer is that Ungern was a total bastard, in the non-technical sense, and so were most of those he fought with and against. Like the Russian Civil War that provides the backdrop to their story, these characters are, at best, a study in unredeemed villainy.

To his credit, Palmer resists injecting any faux heroism for the sake of story structure. In its absence, the closest thing to a hero here is Central Asia. Ungern's chosen canvas, from the rugged mountains of Transbaikal to the limitless grasslands of Mongolia itself, is impossibly romantic for anyone with a penchant for wide open spaces, even if the man himself becomes their heart of darkness.

We are introduced to him as a teenage psycho, expelled from every elite school on which his family inflicts him. “I imagine him not to have been a bully as such,” Palmer writes, “but...rather one of those pupils of whom even bullies are afraid, the kind who violate the unwritten rules of childhood fights, whom nobody wants to sit near, and who cannot be trusted with compasses or scissors”.

Brief service in the Russo-Japanese war impressed Ungern far more than any school rule, and the killing fields of the First World War annealed him: he fought with such suicidal bravery that some said he survived by reducing his enemies to astonished observers. The Russian Revolution destroyed his world, but the treaty of Brest-Litovsk, which ceded vast tracts of western Russia to Germany, galvanised him into murderous action on the counter-revolutionary front line.

That line was the Trans-Siberian railway. One of this book's most fascinating digressions describes the armoured trains that chugged back and forth across Asia during the civil war as dreadnoughts of the land. Ungern commanded one of them in Transbaikal, razing whole villages from his steel-plated gun carriages, until the remorseless Red advance drove him to Mongolia.

On the Mongolian steppe, in winter temperatures of -40C, thousands of miles from anything he might have called home or anyone who might have been a friend, Ungern unleashed his inner demons. He commanded a ragged force of a few thousand desperate souls with unimaginable cruelty, executing suspected traitors on the spot if they were lucky, or tearing them apart by tying them to trees bent towards the ground and then released. In early 1920 he drove the Chinese from the ancient city of Urga, but didn't hold it for long. By 1921 it was all over. Hunted down by the Red Army, he was tried and executed in Novosibirsk.

Palmer has written as serious a history as is possible for such an unbelievable subject, without stinting on the gore or dodging the big, awkward questions Ungern raises about the capacity of humans to revere monsters. As a result, this particular monster has been retrieved from obscurity. The ghosts of his victims might call this undeserved, but readers will not complain.

The Bloody White Baron by James Palmer
Faber, £18.99; 272pp

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