Once a small regional clan from Izu Province, a provincial fiefdom of Yorimasa MINAMOTO of the Settsu-Genji (a branch of the Minamoto clan) in the late Heian period, the Hojo clan followed the army raised by Yoritomo MINAMOTO of the Kawachi-Genji (another branch of the Minamoto clan), who had been exiled to Izu, and formed a bakufu with Yoritomo as the seii taishogun (literally, the great general who subdues the barbarians).
平安時代末期に摂津源氏の源頼政の知行国だった伊豆国の小豪族に過ぎなかった北条氏は、伊豆へ流罪となっていた河内源氏の源頼朝の挙兵に従い、頼朝を征夷大将軍とする幕府を成立させる。