From Wikipedia

The Mongol Empire

The Mongol Empire  was an empire from the 13th and 14th century spanning from Asia across Eastern Europe. It is the largest contiguous empire in the history of the world; emerging from the unification of Mongol and Turkic tribes in modern day Mongolia, and grew through invasions, after Genghis Khan had been proclaimed ruler of all Mongols in 1206. At its greatest extent it stretched from the Danube to the Sea of Japan and from Arctic to Camboja, covering about 33.0 million km² (in 1279), one fifth of the Earth's total land area, and held sway over a population of over 100 million people at that time. It is often identified as the "Mongol World Empire" because it spanned much of Eurasia. Under the Mongols new technologies, various commodities and ideologies were disseminated and exchanged across Eurasia.