Man has always sought to acquire information regarding his enemies, rivals, even allies, in order to understand their motivations, predict their actions, and behave according to the best of his own interests. In the Bible, we are told that Yahveh ordered Moses to send spies to the land of Canaan. Sun-Tzu's treatise on war, written five centuries B.C., comprises a chapter on intelligence. Leo VI's Taktika insist upon the importance of intelligence, while the Thousand and One Nights contains numerous accounts of Byzantine intelligence operations. Thanks to his spy-networks, the Mongol ruler Subotaï was well aware of conditions prevailing in Christian Europe. Moctezuma's spies kept him well informed as to the strength and whereabouts of the Spanish invaders. Francis Walsingham, Elizabeth l's chancellor, had set up a formidable intelligence service. As Hobbes put it, “spies are no less important to the sovereign than rays of light to the human soul for the discernment of visible objects.”