How did the Mongol Empire Spread?

Originating in the steppes of Central Asia, the Mongol Empire eventually stretched from Central Europe to the Sea of Japan, extending northwards into Siberia, eastwards and southwards into the Indian subcontinent, Indochina, and the Iranian plateau, and westwards as far as the Levant and Arabia.

The Mongol Empire emerged from the unification of nomadic tribes in the Mongols homeland under the leadership of Genghis Khan, who was proclaimed ruler of all Mongols in 1206. The empire grew rapidly under the rule of him and his descendants, who sent invasions in every direction.