Precursors to the Ōnin War

Timeline

1. 1451–1455Kyoto · KinkiShikken Hosokawa Katsumoto and western daimyō Yamana Sōzen confronted each other in shogunal politics, each courting the Shiba, Hatakeyama, and Ise shugo families. They repeatedly clashed over court appointments and shogunal rulings; the rudiments of the Eastern and Western armies were faintly visible by the mid-1450s.
2. 1455–1460Kyoto · KinkiSuccession disputes among the Shiba (Yoshimune vs. Yoshitoshi) and Hatakeyama (Yoshitomo vs. Yoshitsuna) continued unabated, with Hosokawa and Yamana each intervening on behalf of different heirs. Shogunal rulings repeatedly proved ineffective, warrior private warfare and Kyoto's public security worsened, becoming one of the direct triggers of the later Ōnin War.
3. 1458–1460Kyoto Imperial Palace · KinkiAshikaga Yoshimasa had no son, and arrangements for shogunal succession became the core issue of the Hosokawa–Yamana contest. Both sides used the heir question to win allies and exclude rivals, and the shogunate could no longer mend the rift. By around 1460, the opposing alliances of Kyoto's warrior groups were essentially formed, and large-scale civil war was imminent.