Since prehistoric times, warlords and chiefs have recognised the importance of inducing psychological terror in opponents. Facing armies would shout, hurl insults at each other and beat weapons together or on shields prior to an engagement, all designed to intimidate the enemy. Massacres and other atrocities were certainly first employed at this time to subdue enemy or rebellious populations or induce an enemy to abandon their struggle. Currying favour with supporters was the other side of psychological warfare, and an early practitioner of such this was Alexander the Great, who successfully conquered large parts of Europe and the Middle East and held on to his territorial gains by co-opting local elites into the Greek administration and culture. Alexander left some of his men behind in each conquered city to introduce Greek culture and oppress dissident views. His soldiers were paid dowries to marry locals[8] in an effort to encourage assimilation. Genghis Khan, leader of the Mongolian Empire in the 13th century AD employed less subtle techniques. Defeating the will of the enemy before having to attack and reaching a consented settlement was preferable to actually fighting. The Mongol generals demanded submission to the Khan, and threatened the initially captured villages with complete destruction if they refused to surrender. If they had to fight to take the settlement, the Mongol generals fulfilled their threats and massacred the survivors. Tales of the encroaching horde spread to the next villages and created an aura of insecurity that undermined the possibility of future resistance.[9] The Khan also employed tactics that made his numbers seem greater than they actually were. During night operations he ordered each soldier to light three torches at dusk to give the illusion of an overwhelming army and deceive and intimidate enemy scouts. He also sometimes had objects tied to the tails of his horses, so that riding on open and dry fields raised a cloud of dust that gave the enemy the impression of great numbers. His soldiers used arrows specially notched to whistle as they flew through the air, creating a terrifying noise.[10] Another tactic favoured by the Mongols was catapulting severed human heads over city walls to frighten the inhabitants and spread disease in the besieged city's closed confines. This was especially used by the later Turko-Mongol chieftain. The Muslim caliph Omar, in his battles against the Byzantine Empire, sent small reinforcements in the form of a continuous stream, giving the impression that a large force would accumulate eventually if not swiftly dealt with. In the 6th century BCE Greek Bias of Priene successfully resisted the Lydian king Alyattes by fattening up a pair of mules and driving them out of the besieged city.[11] When Alyattes' envoy was then sent to Priene, Bias had piles of sand covered with corn to give the impression of plentiful resources. This ruse appears to have been well known in medieval Europe: defenders in castles or towns under siege would throw food from the walls to show besiegers that provisions were plentiful. A famous example occurs in the 8th century legend of Lady Carcas, who supposedly persuaded the Franks to abandon a five-year siege by this means and gave her name to Carcassonne as a result.