Banners during the Warring States period. Banners were used for the discrimination of ally and foe on the battlefield. In Heian period. it had been common to use red and white flags; e.g., Genji used white flag and Heishi used red flag. As far as the discrimination was needed amongst only two sides, there were no troubles in using only two military banners, however, “Ie” of various kinds of family names appeared. and subdivision of a family name had occurred. For instance, Ashikaga-shi and Nitta-shi from Gen-ji family, Houjyo-shi and Chiba-shi from Hei-shi family. Therefore, banners were introduced for the discrimination of those various “ie”s on the battlefields. Because the group tactics by foot soldiers had become a mainstream tactic during Warring States period, even if the generals knew each other, the soldiers couldn’t discriminate ally and foe, therefore unique banners were invented. Takeda Shingen used Fu-rin-ka-zan flag mark quoted from Sun-tzu, Uesugi Kensin put a Chinese character “Bi” from the name of the god of war “Bi-sha-mon-ten”. Family crest and illustration is also sometimes used for banners.