Excerpts from Books and Wikipedia
Yamana clan against Hosokawa clan; "The Onin War (...) was a civil war that lasted 10 years (1467–1477) during the Muromachi period in Japan. A dispute between Hosokawa Katsumoto and Yamana Sozen escalated into a nationwide war involving the Ashikaga shogunate and a number of daimyo in many regions of Japan.
The war initiated the Sengoku jidai, "the Warring States Period". This period was a long, drawn-out struggle for domination by individual daimyo, resulting in a mass power-struggle between the various houses to dominate the whole of Japan. During this long period three individuals emerged who would unite Japan under one rule; they were Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu." [Wikipedia] "First of many significant civil wars between shogunates that would continue for another century during the Muromachi period." [Wikipedia: Timeline of Middle Ages]