Before the establishment of the Tokugawa Shogunate(江戸幕府), a six-hour battle took place on October 21, 1600. This was called the ‘Battle of Sekigahara'(関ヶ原の戦い), a savage conflict which changed the course of Japanese history forever …
Since the death of the preeminent daimyo, warrior, general, samurai and politician Toyotomi Hideyoshi, men of noble birth continued feuding for absolute power in Japan. Factions began to emerge which even divided the people. In order to put this to an end, the two most powerful contenders (Tokugawa Ieyasu and Ishida Mitsunari), agreed to a decisive battle. The Tokugawa forces were called ‘Army of the East’ while Ishida’s forces were called ‘Army of the West’. Initially, the Army of the West outnumbered the Army of the East but later on their numbers decreased. The Western army disintegrated with the commanders fleeing and scattering. Ishida was then captured and later on executed. Tokugawa Ieyasu’s success allowed them to redistribute the fiefs to the participants. He gave rewards to those who supported him and punished those who fought against him.
(Via Japan Info)
I may be wrong but I think this is the time frame of the James Clavell novel Shogun.
Want to see a reenactment?
A simulation of this war can be seen in the quiet farming village of Sekigahara. The momentous event is recreated in a somewhat bizarre theme park called “Sekigahara War Land.” This is where people can discover and experience the atmosphere of the battle.
Check out the article for the details. Looks interesting.