Minamoto no Yoshitsune (源 義経?, 1159 – June 15, 1189) was a general of the Minamoto clan of Japan in the late Heian and early Kamakura period. ... He is considered one of the greatest and the most popular warriors of his era, and one of the most famous samurai fighters in the history of Japan. The legends that deal with his public career show Yoshitsune as a great, virtuous warrior. He was often shown as kind to those around him and honorable, but he was also shown as short-tempered, tactless, blunt, and naive....After the Genpei War, Yoshitsune joined the cloistered Emperor Go-Shirakawa against his brother Yoritomo. Fleeing to the temporary protection of Fujiwara no Hidehira in Mutsu again, Yoshitsune was betrayed, defeated at the Battle of Koromo River, and forced to commit seppuku along with his wife and daughter, by Hidehira's son Fujiwara no Yasuhira...
Some tales however tell of Minamoto's no Yoshitsune escaping his pursuers; fleeing into the wilds of Mongolia; where he lived on under a new name, Temujin; known also as Genghis Khan
(From Wikipedia).