The steppes of Mongolia are flat lands that seem to stretch forever. Horses enjoy the open land and have become the partners of men who live there and need their help traveling the long distances between habitations. The open ground is subject to extremes of temperature and of weather; agriculture does not flourish there but living by the horse does. Moving from place to place to vary the grazing land, living in large felt tents to keep out the elements and living on fermented mare's milk and meat from herd animals, the life of nomads has in many ways changed little over many centuries. Land is valuable to nomad tribes for what it offers and that offering quickly disappears as the horses and other animals eat the available foliage. Hence, there is always a pressure to move on and hence always a pressure to fight with other tribes and control their territories, forcing them to move on to less attractive lands.
This pattern had continued for hundreds of years and displaced tribes had moved west, terrorizing the sedentary tribes that had the misfortune to stand in their way. The Huns, the Bulgars, the Avars and the Magyars were just some of the tribes who carved out large temporal empires for themselves in eastern Europe and even attacked the western powers. These empires rarely proved to be durable as the nomads were themselves too few to sustain them beyond the initial terror of their arrival and their frequent slaughter of peasant farmers that destroyed their predecessors.
Temujin, a Mongol prince born in 1164 near to the traditional Mongol capital of Karakorum, knew all of this and had a somewhat more ambitious goal. First he would unite all of the Mongol tribes. Since one displaced tribe of Mongols could cause such devastation, then surely uniting all of them would create a fighting force that would conquer the world? There may only have been some 700,000 Mongols but their highly mobile form of warfare, based on their ability with horses and with powerful bows that could outshoot most of their contemporaries, represented a potent fighting force that could sweep away most enemies. Not only that but when other people were conquered, such as the Turkish tribes on the fringes of Mongol territory and the numerous Chinese to the east and south, then they could be recruited into the armies, albeit in subordinate roles. Further, the Chinese could be used to administer their own lands, for the benefits of the Mongols, especially Temujin who could dedicate himself to the horse and siring a new tribe of offspring.