Out of the misty Mongolian steppes emerge 5,000 snarling, scimitar-wielding horsemen in 13th-century battledress. Who said the BBC was strapped for cash? In fact, this cast of thousands was lent to the producers of STORM FROM THE EAST (9.45pm BBC2), a four-part documentary on the Mongol empire, by the Mongolian Ministry for Arts, which was making a feature film about Genghis Khan. The break-up of the Soviet Union has seen the resurgence of Genghis Khan as a symbol of Mongolian nationalism (as well as facilitating the shooting of this series in a previously inaccessible area). Birth of an Empire, the first part of Robert Marshall's thorough series, charts the rise of the Mongols from an anonymous tribe of nomadic shepherds to rulers of a region twice the size of the Roman Empire. Under the leadership of Genghis Khan, the Mongols were ferociously hardy (even today the tribesmen survive unforgiving winters on the steppes using dried animal dung as fuel). But the key to their success lay in terror tactics; such was the Mongols' reputation for ravaging, nations surrendered virtually at the mention of Genghis's name. Eat your heart out, 'Chelsea Headhunters'.