The Mongols were a collection of nomadic tribes in the Central Asian steppes that unified and expanded under the rule of Genghis Khan to become the largest contiguous land empire to ever exist. Genghis Khan led an incredibly efficient and brutal escapade that conquered lands from northern China all the way to Persia. His sons and grandsons continued these conquests to extend the power of the Mongols into Russia, China, and the Middle East. Although the Mongols brutally destroyed cities in their path, they set up religious tolerant and protected societies once all enemies were killed. This allowed for trade along the Silk Roads to expand dramatically, which spread ideas, people, and disease across Eurasia.