Excerpts from Books and Wikipedia
"The history of Japan in the twelfth century is dominated by the rivalry between two clans of samurai warriors, the Taira (or Heike) and the Minamoto (or Genji), who vied to control the imperial court at Kyoto. . . . After they were driven out of Kyoto in 1183, the Taira retreated to the island of Shikoku to plan a counterinvasion. . . . Yoritomo founded a military government at Kamakura, taking the title shogun ('generalissimo') in 1192. The emperors continued to reign from Kyoto, but in practice Japan would be ruled by shoguns until 1868." [1001 Days]