While the Kins were absorbed in their contest with the Southern Chinese, they were oblivious of the growth of a new and formidable power on their own borders. The strength of the Mongols had acquired serious dimensions before the Kins realized that they would have to fight, not only for supremacy, but for their very existence. Before describing the long wars that resulted in the subjection of China by this northern race, we must consider the origin and the growth of the power of the Mongols, who were certainly the most remarkable race of conquerors Asia, or perhaps the whole world, ever produced.

The home of the Mongols, whose name signifies "brave men," was in the strip of territory between the Onon and Kerulon rivers, which are both tributaries or upper courses of the Amour. They first appeared as a separate clan or tribe in the ninth century, when they attracted special attention for their physical strength and courage during one of China's many wars with the children of the desert, and it was on that occasion they gained the appellation under which they became famous. The earlier history of the Mongol tribe is obscure, and baffles investigation, but there seems no reason to doubt their affinity to the Hiongnou, with whose royal house Genghis himself claimed blood relationship. If this claim be admitted, Genghis and Attila, who were the two specially typical Scourges of God, must be considered members of the same race, and the probability is certainly strengthened by the close resemblance in their methods of carrying on war. Budantsar is the first chief of the House of Genghis whose person and achievements are more than mythical. He selected as the abode of his race the territory between the Onon and the Kerulon, a region fertile in itself, and well protected by those rivers against attack. It was also so well placed as to be beyond the extreme limit of any triumphant progress of the armies of the Chinese emperor. If Budantsar had accomplished nothing more than this, he would still have done much to justify his memory being preserved among a free and independent people. But he seems to have incited his followers to pursue an active and temperate life, to remain warriors rather than to become rich and lazy citizens. He wrapped up this counsel in the exhortation, "What is the use of embarrassing ourselves with wealth? Is not the fate of man decreed by heaven?" He sowed the seed of future Mongol greatness, and the headship of his clan remained vested in his family.

In due order of succession the chief ship passed to Kabul Khan, who in the year 1135 began to encroach on the dominion of Hola, the Kin emperor. He seems to have been induced to commit this act of hostility by a prophecy, to the effect that his children should be emperors, and also by discourteous treatment received on the occasion of his visit to the court of Oukimai. Whatever the cause of umbrage, Kabul Khan made the Kins pay dearly for their arrogance or short-sighted policy. Hola sent an army under one of his best generals, Hushahu, to bring the Mongol chief to reason, but the inaccessibility of his home stood him in good stead. The Kin army suffered greatly in its futile attempt to cross the desert, and during its retreat it was harassed by the pursuing Mongols. When the Kin army endeavored to make a stand against its pursuers, it suffered a crushing overthrow in a battle at Hailing, and on the Kins sending a larger force against the Mongols in 1139, it had no better fortune. Kabul Khan, after this second success, caused himself to be proclaimed Great Emperor of the Mongols. His success in war, and his ambition, which rested satisfied with no secondary position, indicated the path on which the Mongols proceeded to the acquisition of supreme power and a paramount military influence whithersoever they carried their name and standards. The work begun by Kabul was well continued by his son Kutula, or Kublai. He, too, was a great warrior, whose deeds of prowess aroused as much enthusiasm among the Mongols as those of Coeur de Lion evoked in the days of the Plantagenets. The struggle with the Kins was rendered more bitter by the execution of several Mongols of importance, who happened to fall into the hands of the Kins. When Kutula died the chiefship passed to his nephew, Yissugei, who greatly extended the influence and power of his family among the tribes neighboring to the Mongol home. Many of these, and even some Chinese, joined the military organization of the dominant tribe, so that what was originally a small force of strictly limited numbers became a vast and ever-increasing confederacy of the most warlike and aggressive races of the Chinese northern frontier. Important as Yissugei's work in the development of Mongol power undoubtedly was, his chief historical interest is derived from the fact that he was the father of Genghis Khan.