Along with the
Minamoto, Taira was one of the honorary surnames given by the emperors of the
Heian period (794–1185) to their children and grandchildren who were not considered eligible for the throne. Some grandchildren of Emperor Kanmu were the first to bear the name of Taira, after
825. Later, descendants of
Emperor Ninmyō,
Emperor Montoku and
Emperor Koko also received the surname. The specific hereditary lines of these emperors are referred to by the posthumous name of the emperor followed by Heishi, for example
Kanmu Heishi. The Kanmu Heishi line has two major branches. One was founded in
889 by
Taira no Takamochi (great-grandson of the 50th Emperor Kanmu, who reigned from
781 to
806) and proved to be the strongest and most dominant line during the
Heian period. A great-grandson of Takamochi,
Taira no Korehira, moved to
Ise Province (currently part of
Mie Prefecture) and established an important
Daimyo dynasty.
Masamori, his grandson; and
Tadamori, his great-grandson, became loyal supporters of
Emperor Shirakawa and
Emperor Toba, respectively. Later, Tadamori's son,
Taira no Kiyomori, created what was considered the first
samurai government in the history of Japan. Taira no Kiyomori, son and heir of Tadamori, rose to the position of
Daijō Daijin (great Minister of State), after his victories in the
Hōgen Rebellion (1156) and the
Heiji Rebellion (1160). This branch of the Kanmu Heishi had many collateral branches, including
Hōjō,
Chiba,
Miura and
Hatakeyama. == Genpei War ==