The History of the Sekigahara War – A Defining Chapter in Shogun History

The period from 1467 to 1590 in Japan was known as the Warring States period. During this time, Japan was ravaged by war as samurai lords battled each other for territory and influence over the Imperial court. It’s the era that made samurai into legends, immortalized in the films of Kurosawa Akira.

Although the Imperial court held onto the ceremonial trappings of government, real power had long since passed into the hands of the shogun—a military leader nominally appointed by the Emperor. By the 13th century, a series of ineffective shoguns combined with growing economic pressures had caused the shogun’s influence to wane, leaving powerful samurai warlords free to pursue their own ambitions.

As the Warring States period drew to a close, three such warlords emerged with the power and strategic vision to unite the country. The first, Oda Nobunaga , began this epic task through a series of spectacular military campaigns, ultimately toppling the Ashikaga shogunate and ruling over 20 provinces in central Japan before his sudden death in 1582.

Nobunaga’s army and territory passed to his retainer, Toyotomi Hideyoshi, who not only succeeded in unifying the country but went further still, marshaling a vast samurai army in two attempted invasions of the Korean peninsula. Despite all his power, Hideyoshi could do little to ensure the succession of his young son, Toyotomi Hideyori.

When Hideyoshi passed away in 1598, his former ally Tokugawa Ieyasu schemed to take power for himself, forming alliances with other powerful warlords in the east. Opposing him was the Toyotomi loyalist Ishida Mitsunari and a growing coalition of samurai lords united in their mistrust and hatred of Ieyasu.

In October of 1600, with Ieyasu’s attention focused on a rebellion to the north, Mitsunari and his allies seized the opportunity to raise their own army. Following a series of smaller skirmishes, the two sides met on the plain of Sekigahara, where the Mitsunari’s army hoped to block Ieyasu’s return to the capital.

Early on the morning of October 21, the Eastern Army led by Ieyasu himself arrived on the plain under cover of thick fog. Under Mitsunari’s command, the numerically superior Western Army awaited them in the hills to the northwest of the valley in a strong defensive position. Despite these apparent advantages, Mitsunari found himself in a precarious position. More a politician than a warrior, Mitsunari had never quite gained the respect of his samurai peers, causing some of his allies to bristle at his commands. To make matters worse, Ieyasu had sent out a storm of letters offering land and titles to any western leaders willing to switch sides.

By 8 am, the fog had cleared enough for both sides to see each other. Soon, shots rang out and the battle for the future of Japan had begun. At first, things were going okay for the Western Army, but Mitsunari soon ran into difficulty as orders went unanswered, leaving sections of the army out of his control. At 11 am, under heavy attack, Mitsunari lit a signal flare—the predetermined signal for an all-out attack by the western forces. At this critical moment, however, several western commanders still refused to engage with the enemy. One such commander was 19-year-old Kobayakawa Hideaki, a veteran of Hideyoshi’s Korean campaign.

Despite promising Ieyasu that he would switch sides, Kobayakawa was unsure of what to do and held his position on Mount Matsuo. Finally losing his patience, Ieyasu moved his own encampment forward and fired a volley of warning shots at Kobayakawa, forcing the young turncoat to act. Kobayakawa’s army poured down the mountainside and clashed with their former allies, causing several other western leaders to defect and the Western Army to collapse in a devastating chain reaction.

The Battle of Sekigahara was one of the most decisive engagements in Japanese history, bringing the Warring States period to an effective close. Mitsunari fled the battlefield but was captured soon after and executed in Kyoto, defiant to the last.

Ieyasu further solidified his position and was named shogun in 1603, ushering in a Tokugawa dynasty that would endure for 260 years. Hideyoshi’s family would continue to be a thorn in Ieyasu’s side until they were finally wiped out in 1615 at the Siege of Osaka Castle.

Apart from changing the course of history, the battle has left a lasting impression on Japanese culture, from the phrase “tenkawakeme,” meaning a fateful, decisive moment, to the combatants themselves—many of whom can be found in books, film, anime, and even video games.

Perhaps most profoundly of all, Sekigahara still marks the dividing line between eastern and western Japan. A host of cultural differences distinguish the two, such as recipes for soup stock and which side of the escalator people stand on.