Genpei Kassen (源平合戦, Literally: Genpei War) is a historical simulation strategy game which focuses on the war between the Genji (Minamoto clan) and the Heike (Taira clan) at the end of Japan's Heian period (12th century).
Heike Monogatari serves as the game's prominent reference, but other folktales and fictional stories are integrated as well. References to events found within historical records are present but are often overshadowed by episodes made popular by romantic fiction.
Unlike other historical simulations at the time of its debut, Genpei Kassen has remained primarily for personal computers. It's not as popular as a result.
The player can only command figures from the Ise-Heishi, Seiwa-Genji, or Oshu-Fujiwara clans in each scenario; other clans and forces of the war are controlled by the game's AI. Although the influence each clan has changes depending on the scenario, each clan has a set of general traits to distinguish themselves:
Seiwa-Genji - mighty warriors with strong ties of loyalty; diminutive supplies and no trade threatens domestic security; specialize in archery
Ise-Heishi - high political influence and excellent domestic trade; constantly harassed by multiple rivals in most scenarios; excel in naval warfare
Oshu-Fujiwara - distant from warfare in most scenarios; rich domestic and economical resources yet lacks capable generals for war