Genghis Khan was the leader of a destitute clan who prevailed in an inter-clan feud. He overcame all rivals and by 1206 was acknowledged as Genghis Khan (Universal Ruler) of all Mongolian people. He became one of the most supreme military leaders in the world. He subjected China, devastated Khwarezm (Uzbekistan) and became the creator of the Mongol nation and founder of one of the vastest empires in world history which stretched from Northern China to the Black Sea.
The success of the Mongol armies was the result of superior strategy, a highly mobile cavalry, endurance, discipline and a co-ordinated manner of fighting. They succeeded in the only successful winter invasion of Russia when the Mongol army moved with great speed on the frozen rivers - transforming an obstacle into a speedway to surprise the enemy.
The Mongols were not a numerous people, but from the outset Genghis Khan augmented his armies from Turkish tribes until the Turks in the Mongol armies outnumbered the native Monogols. Thus the Turkish language advanced across Asia with the Mongol armies. To communicate across their empire the Mongols established a transcontinental mail service creating thus a crucial bridge between East and West.
After the death of Genghis Khan the Empire was divided between his four sons: Jagatai, Tului and Ugudei. Each received 'ulus' (military levies), a 'jurt' (grazing area) and 'ingus' (a share in the tribute). Karakorum became the permanent capital.
The Great Khan Ugudei completed the subjugation of Northern China.