The Mongols united through a great leader and warrior who took the name Ghengis Khan. They invaded China, took power and increased their empire throughout the world. The offspring and Relatives of Ghengis, were given large kingdoms to rule. An efficient Governing system kept them successful financially. Many other tribes and people moved west to escape them, causing a mass migration all the way to Ireland. The Saxons and the Celts were among those that migrated west to the British Isles. All of this affected the population of Europe, the near east and practically all the known world at that time.