Sengoku Period

Also known as the Age of the Warring States, this period lasted for about 250 years years, from around the mid 1400's to the early 1600's.  This period ended when Tokugawa Ieyasu beame Shogun in 1603.  This is one of the most confusing times in Japanese history. The Ashikaga clan controlled the shogunate, but really hadn't secured the loyalty of many daiymos, thus weakening their power.  This is an age where local warlords fought each other to expand their territory.  Eventually, Oda Nobunaga would rise as the dominant warlord, unifying about a third of Japan.  He was asssassinated by one of his own generals, paving the way for Hideyoshi Toyotomi, who would unify the nation.  In a cumming move, Tokugawa Ieyasu usurped power from the Toyotomi clan and became Shogun, thus ending the period and Japan entered a new period known as the Edo period.

Many of the books and movies during this period focus on stories involving either Takeda Shingen or Oda Nobunaga.