The story of the Khyber Pass, the narrow mountain route which - more than any other single place on earth - has shaped civilisations.Thirty miles long, and in places no more than sixteen metres wide, the Pass is the only natural cutting through the great mountains of the Hindu Kush - and hence the one feasible route from Central Asia into India.Its story - of the rise and fall of empires - begins with Cyrus and Darius, the great Persian kings. Legendary conquerors soon follow: first Alexander the Great, then, much later, the White Huns (who would bind the heads of their children to make their appearance in battle more frightening) and Genghis Khan. In between are the Ancient Greeks, whose reach spread east to the Pass; and tribes of nomads and barbarians whose civilizations, Paddy Docherty shows, were much more sophisticated than commonly supposed.Here also are mountain warriors and religious visionaries - around the Pass arose three of the great world religions, Buddhism, Sikhism and Islam - as well as artists, poets and scientists.In more recent times, the British army suffered its infamous retreat from Kabul in 1842. The Khyber region is still largely lawless today, a place of gunsmiths and drug markets and the hideout of terrorists. Docherty's own travels in this true frontier - and the continuing presence of US and British troops in Afghanistan - bring the story into the twenty-first century.