In a nutshell, the warring states period actually began eleven years before with the Onin War, 1467 to 1477, and lasted to the beginning of the 17th century. The conflict began in Kyoto, the capital city of Japan from 794 until 1868, and was between two powerful families, the Hosokawa family in the “west “and the Yamana clan in the “east” over shogunal succession. The “Kyoto” war spilled over into the outlying provinces and led to the bloody civil war, labeled” Sengoku”, by historians when the social and political upheaval evolved into a constant military clash between the lesser warlords that pitted samurai against samurai. The conflict ended after the battle of Sekigahara in 1600, when Tokukawa Ieyasu defeated the followers of Toyotomi Hideyori. The unification of Japan finally came about when Emperor Go-Yozei appointed Ieyasu as military leader with the title of Shogun, or bakufu (tent officer) in 1603.
Battle of Kawanakajima in 1561
Japan in the Late 16th Century
Takeda Shingen by artist, Utagawa Kuniyoshi
Takeda Shingen http://en.wikipedia.org/wiki/Takeda_Shingen
Uesugi Kenshin http://en.wikipedia.org/wiki/Uesugi_Kenshin
The Tokugawa Shogunate (1603-1858) http://saznj.tripod.com/
Toyotomi Hideyoshi http://en.wikipedia.org/wiki/Toyotomi_Hideyoshi