The Kessen-ba, at which a monument now stands commemorating the area where the fiercest fighting was said to have taken place. The battle of Sekigahara was fought in October of 1600, between armies commanded by Tokugawa Ieyasu (Eastern Army) and Môri Terumoto (Western Army). Basically, it was a power struggle between the so-called loyalists to the deceased Taiko Toyotomi Hideyoshi, and oppositionists who were loyal to Tokugawa Ieyasu. In reality, however, the divisions were also based on personal likes and dislikes towards the de facto Western Army leader, Ishida Mitsunari. It is considered to be one of the most important battles fought in Japanese history, for a couple of reasons. 

                                                       

                                                            

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It was one of the largest single battles fought, with about 180,000 fighting at Sekigahara itself,                                                        
and about 70,000 fighting related battles and sieges at other venues.                                                         
                                                        

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It would place the victor, Tokugawa Ieyasu, in a position of unquestionable power and authority.                                                        
                                                        

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The outcome of the battle would determine the fates and fortunes of men on both sides;                                                        
Môri Terumoto, for example, would see his power drop to less than a third of its original standing,                                             
 while Kato Kiyomasa would see his wealth double.                                                               

                                                        
                                                        
The names which were present at the battle were overall very impressive: all famous provincial warlords in Japan were either present or played some part in the events leading up to the battle, and thus the cumulative experience of the men at the battlefield was very great. However, Sekigahara lacked the intricacy or strategy present at some other battles of the past. 

This was partly due to the composite makeup of the armies -- men from different clans who were unaccustomed to fighting alongside one another had to do so. It also had to do with the character of the people involved: where turncoats were involved, it was hard to have a set strategy. Finally, it was also partly because there just wasn't enough room or time to have any grand strategy. The result was a huge melee in which the most prevalent set goal was simply to annihilate the other side.