One prominent theory is influenced by the results of the Genpei War (1180–1185). Until the Heian period, the , a symbol of the Imperial Court, had a golden sun circle and a silver moon circle on a red background. At the end of the Heian era, the Taira clan called themselves a government army and used the red flag with a as per the Imperial Court. The Genji (Minamoto clan) were in opposition so they used a white flag with a when they fought the Genpei War (1180–1185). When the Taira clan was defeated, the was formed by the Genji. The warlords who came after such as Oda Nobunaga and Tokugawa Ieyasu realized they were successors of Genji, and so raised the flag in battle.
One prominent theory is influenced by the results of the Genpei War (1180–1185). Until the Heian period, the , a symbol of the Imperial Court, had a golden sun circle and a silver moon circle on a red background. At the end of the Heian era, the Taira clan called themselves a government army and used the red flag with a as per the Imperial Court. The Genji (Minamoto clan) were in opposition so they used a white flag with a when they fought the Genpei War (1180–1185). When the Taira clan was defeated, the was formed by the Genji. The warlords who came after such as Oda Nobunaga and Tokugawa Ieyasu realized they were successors of Genji, and so raised the flag in battle.