Harun al-Rashid, the legendary caliph portrayed in The Thousand and One Nights, was the son of a Yemenite slave who cleared Harun’s path to power, very probably by poisoning her eldest son.Harun reigned for a quarter of a century, his empire spreading over south-west Asia and into north Africa. He waged war on the Byzantine Empire, and dealt ruthlessly with the religious and social insurrections which threatened his kingdom, executing almost the entire Barmakid family when they threatened to become too powerful.As well as being a ruthless soldier and politician Harun was also a great patron of the arts, and highly esteemed by Charlemagne. He turned Baghdad into a brilliant centre of culture and learning, which witnessed unprecedented economic...