There is a lot of controversy surrounding the way Genghis Khan conquered his empire. When he would approach an enemy city, he would give them the option of joining his forces or being destroyed. At first many would decline his offer to join him, but later, as survivors from the massacres that happened at those cities returned, many would chose to join him. Fear was a tactic he used and he didn't just kill men, he let his soldiers loose to kill everyone. Another great controversy, about his genetic legacy, was that he had the opportunity to rape a lot of women, which could've made the 0.5% of people we think are related to him today.