The Mongol Empire began when various Mongol tribes united under the leadership of Chinggis Khan in the early 13th century. Chinggis Khan established a large nomadic empire through military conquest and instituted a legal code for the tribes. The Mongol Empire went on to become the largest contiguous land empire in world history, stretching from Eastern Europe to the Sea of Japan. It later fractured into smaller khanates, including the Golden Horde that conquered parts of Russia and Eastern Europe. While the Mongols initially practiced religious tolerance, persecution of other faiths like Christianity increased as Islam became dominant in the later Mongol Empire.