Gempei War

The Gempei War which took place between 1180 and 1185 was a national civil war between the Taira and Minamoto clans during the late Heian period of Japan. It resulted in the downfall of the Taira and the establishment of the Kamakura shogunate under Minamoto no Yoritomo, who appointed himself as Shogun in 1192, governing Japan as a military dictator from the eastern city of Kamakura.

The name Gempei or Genpei comes from the words Minamoto (Gen) and Taira (Hei, which was pronounced as pei)
These two families were fierce rivals, both were ancient families, descended from royalty.
The Heike or Taira had close ties with the court, and were well known as accomplished artists and men of letters as well as great warriors.
The Genji or Minamota were rustics, and each side derided the other for their chosen lifestyles.