Ōnin War participant Yamana clan
Origin
The Ōnin conflict began as a controversy over who would succeed shōgun Ashikaga Yoshimasa. In 1464, Yoshimasa had no heir. He persuaded his younger brother, Ashikaga Yoshimi, to abandon the life of a monk, and named him heir. In 1465, the unanticipated birth of a son to Yoshimasa put these plans in question. The infant, Yoshihisa, led to a succession crisis with two competing factions. On one side was the shōgun and his brother, together with the shōgun's deputy, Hosokawa. On the other side was Yoshihisa's mother, Hino Tomiko, and her ally Yamana, who was the governor of several provinces.: 220 Tomiko sought political and military support to rule as regent until the birth of her son, the future shogun Ashikaga Yoshihisa. She secured the support of Yamana Sōzen and other leaders of powerful samurai clans. In contrast to Tomiko and Yamana, Yoshimi had the support of the Hosokawa clan, a powerful clan that had a great influence on the shogunate court. This dispute for succession started the Ōnin War and led to the beginning of the Sengoku period.Hosokawa had always worked closely with the shōgun's brother Ashikaga Yoshimi, and supported his claim to the shogunate. Yamana took this as an opportunity to oppose Hosokawa further, supporting the child as heir to the shogunate. War broke out in the city of Kyoto. This was regarded by the Ashikaga shōgun as an act of rebellion, and thus the Ashikaga and their supporters were forced to try to stop it. The Ashikagas tried to prevent the outbreak of war over the next heir, but the situation escalated into a war that designated the leader of the victorious party as the next shōgun. In 1467 the uncertainty had caused a split amongst the warrior clans, and the succession dispute became a pretext for a struggle for military supremacy. In the end, there was no clear-cut winner. The complex array of factional armies simply fought themselves into exhaustion.