As horsemen they were highly skilled, a golden horde flowing out of the East. The weapons they carried were formidable - arrows that could penetrate armour and siege engines that could storm cities. Their messengers, changing from pony to pony, could ride 200 miles in a day. As conquerors they were the most lethal warriors on earth.

The hard men of Mongolia had an exceptional leader. John Man's Genghis Khan: Life, Death and Resurrection is an exceptional book. Its premise is that the Khan and his heirs united much of the Eurasian world to the degree that he is revered in the East today as a demi-god. It is a vast and brutal story of a tribe from a valley creating an empire larger than that of Alexander or the Romans, carving out a fiefdom from the Pacific to the Middle East, devastating China and Russia and reaching the gates of Europe.

Genghis Khan achieved all this with a notorious cruelty. Anyone who opposed him was slaughtered, his archers glorying in the blood of their enemies, wringing "tears from the womenfolk and bedding their daughters". John Man's history transforms Genghis Khan from a provincial raider into a visionary ruler who gave Asia a more constructive future and opened a trade route between East and West.

Man softens the harshness of the terrain and the plundering with accounts of his own wanderings in Mongolia. But coming out of this valuable reflection on a remote area of the world is Genghis Khan's sense of destiny, finally bringing peace to the silk roads and an enrichment to other civilisations. But at a price.

"Heaven is weary of the inordinate luxury of China," he preached. The world would live fearfully in the shadow of this warning.

If there is a mantle bequeathed by the 13th-century Mongols, it is almost certainly inherited by the Cossacks, who were themselves great horsemen. Dominating the Steppes of Russia, they were fiercely loyal to the Tsars and yet supremely independent. They were the thorn in Napoleon's side in his Snow-bound retreat from Moscow and wielded sabres to crush revolution on the steps of the Winter Palace in St Petersburg. They well earned the epithet of the "vultures of the battlefield", as former British diplomat John Ure shows in his lavishly illustrated The Cossacks (Duckworth, £30). This is a book of startling beauty as well as an ideal probe into the lives of a tragic but romantic people who became victims of Stalin's purges after the Second World War. It's good to remember them dancing to the strains of the balalaika and as the heroes of Tolstoy and Pushkin. John Ure offers it all -- the cruelty and courage, the pride and the poetry, depicted in a brilliant range of words and pictures.

Still dramatically in Asia, Duel in the Snows (John Murray, £20) by Charles Allen is an extremely welcome return to the Younghusband expedition to Lhasa in 1904, when medieval mysticism was conflonted by the mightiest power in the world. Allen, one of the best narrators of Britain's imperial history in India, portrays Younghusband as an obsessive leader who defied Whitehall decrees at every turn, challenging the high passes of Central Asia to bring the secretive Tibetans, ruled by a lama incarnate, under British dominion, using illusory Russian designs as a fuse for his actions.

The whole tragic episode - highlighted by a massacre of 500 Tibetans - is superbly unfolded by Allen, marching intrepidly with the soldiers into the Forbidden City, the elusive prize of Empire.

As one of the boldest episodes in Britain's repertoire of imperial ambitions -- on a scale with Napier's assault on the heights of Magdala in Ethiopia - this is an exciting story with brutal if diplomatic shades of the Khan and the Cossacks.

By Colin Gardiner