Yamana Souzen (山名宗全 1404-1473), originally Yamana Mochitoyo (山名持豊) before becoming a monk. He was one of the Daimyo who fought against Hosokawa Katsumoto during the Onin War in Kyoto.
The Yamana family had seen many defeats over the years, while the Hosokawa family was one of the three families which controlled the position of Kanrei, deputy to the Shogun.
Nevertheless, Yamana, not Hosokawa, was labeled a rebel, and enemy of the state.
Some of Yamana's followers deserted, joining Hosokawa's morally superior side, but many more switched sides as a result of the work of Hosokawa's emissaries to the provinces where Yamana and his allies drew their armies.
A dispute between Hosokawa Katsumoto and YamanaSouzen escalated into a nationwide war involving the Ashikaga shogunate and various daimyo.
YamanaSouzen, referred to as the "Red Monk" for his horrendous temper and his membership of the priesthood, decided to support the infant heir, Yoshihisa.
Both YamanaSouzen and Hosokawa Katsumoto died in 1473, and even then, the war continued on, neither side figuring out how to end the war.