Date(s): October 21, 1600

Armies: Western Army vs. Eastern Army

Victor: Eastern Army

Casualties: Western Army: 5,000-32,000/23,000 defected

Eastern Army: Unknown number

The Battle of Sekigahara was the grand finale of the Sekigahara Campaign and, according to many scholars, was the final battle of the Sengoku Jidai. It was fought between the Western Army, led by Ishida Mitsunari, and the Eastern Army, led by Tokugawa Ieyasu. Sekigahara was the largest samurai battle in Japanese history, and was the largest battle fought on the mainland of Japan.

Before the Battle

The origins of the Battle of Sekigahara begin with the death of the Toyotomi Hideyoshi in September 1598. Hideyoshi’s health began declining in 1590, and had gotten worse by 1598. Before his death, Hideyoshi got his best generals and administrators together to create the go-tairo and the bugyō in August 1598. The generals made up the go-tario and the administrators made up the bugyō. These men were the ones who were supposed to help rule the country until Hideyoshi’s five year old son, Hideyori, became of age (which was fifteen). Not long after Hideyoshi’s death, problems arose with the men left behind to rule the land.

Conflicts began to arise, especially between two prominent figures within the Toyotomi clan: Tokugawa Ieyasu and Ishida Mitsunari. Due to the nature of the times, many samurai did not trust each other, which was one of the main causes for the collapse of the support for the Toyotomi. There was also the fact that the men left behind saw an opportunity to take control of the country for themselves, rather than stand behind a child. One such man who saw things this way was Tokugawa Ieyasu. Ieyasu began to gain power after Hideyoshi’s death, something that Ishida Mitsunari was not fond of. Mitsunari wanted Ieyasu eliminated, however, his scheming and failed assassination attempt resulted in him fleeing Ōsaka Castle, the Toyotomi’s seat of power, dressed as a woman. Despite the situation, Ieyasu granted Mitsunari protection after he begged him to do so, yet, that would not be the end of the problems that would arise. Shortly, after this incident, Hideyori’s guardian, Maeda Toshiie died in the spring of 1599, and the vacancy of the position was taken over by Ieyasu, and he moved into Ōsaka Castle. This was the final straw for Mitsunari. On August 22, 1599, he sent a letter Ieyasu listing thirteen charges to be brought against him, some of which included arranged political marriages that Ieyasu made with his children and that he had taken up Ōsaka Castle as if it were his own. Despite the charges being true, Mitsunari’s complaint was be seen as a declaration of war in the eyes of Ieyasu, and the country was thrown into chaos once more.

With the country divided between the Eastern Army, led by Tokugawa Ieyasu, and the Western Army, led by Ishida Mitsunari, generals who had once served together now had to take a gamble and side with one or the other. Although the battle would not take place until October 1600, there were skirmishes and other problems that arose beforehand. When Ieyasu gathered an army and began to march to his home in Edo, Mitsunari ordered his secret ally, Uesugi Kagekatsu, to attack the Tokugawa Army. When Kagekatsu attacked, however, allies of Ieyasu’s, Date Masamune and Mōgami Yoshiakira, instantly counter-attacked. Another battle that took place before Sekigahara was the Siege of Fushimi Castle, once Hideyoshi’s residence, which later became Ieyasu’s after trading Ōsaka Castle for it. Ishida Mitsunari along with Kobayakawa Hideaki, laid siege to the castle for ten days. In the end, Mitsunari won, but it cost the lives of nearly 3,000 men to take Fushimi from Ieyasu. Other sieges included the Siege of Ueda Castle, Otsu Castle, and Hasedō Castle.

Despite the many sieges and battles that took place before the Battle of Sekigahara, one of the greatest mistakes that happened before the conflict was the handling of the Tokugawa hostages on Mistunari’s part. Mitsunari made hostages of the wives and families that remained in Ōsaka after Ieyasu left for Edo in July 1600. One of these hostages was the wife to Hosokawa Tadaoki, Gracia. Rather than submit to Ishida’s men, however, Gracia ordered a servant to kill her and set fire to their mansion. This shocked many, not just in Ōsaka, but the rest of the country, and it gave many of the wavering Western general much to think about.

The Battle

The Battle of Sekigahara started at eight o’clock in the morning on October 21, 1600. Ishida Mitsunari’s Western Amry outnumbered Tokugawa Ieyasu’s Eastern Forces: with Mitsunari commanding 63,000 and Ieyasu only commanding 57,010. Despite the numerical advantage, the Western Army was not completely together, for many had reservations about fighting under the command of Ishida Mitsunari. There were similar fears in the Eastern Army as well, for generals such as Katō Kiyomasa and Fukushima Masanori were once retainers for Toyotomi Hideyoshi. In fact, it was because of this close relationship that the Eastern general Ii Naomasa, led the first attack on Ukida Hideie’s unit, which was originally supposed to be led by the two previous Toyotomi generals. This cavalry charge into enemy lines made many realize this battle would not be easily won with strategy: it was a melee, pure and simple. This was purely due to the fact that both sides had very headstrong generals that had their own ideas on how the battle would run. One such general with this mentality was Shimazu Yoshihiro, of the Western Forces. When he did not move to the attack, Mitsunari rode out personally to question him for his unit’s inaction. Yoshihiro stated that every daimyo had to do what was best for them at the current moment.

It was not long after Ishida Mitsunari’s encounter with Shimazu Yoshihiro that Tokugawa Ieyasu sent Kuroda Nagamasa to attack Mitsunari’s unit head-on. This was faltered by cannon fire, which only caused confusion for Nagamasa’s unit and for the rest of the samurai in the valley below. It was also around the same time that Mitsunari lit the signal fire to let Kobayakawa Hideaki know that it was time for his unit to advance. His unit never moved. After being spurred into action by Ieyasu, Hideaki finally made his move by defecting to the Eastern Army, and attacking the nearly blind and terribly disabled leper, Ōtani Yoshitsugu. Yoshitsugu was the trusted advisor and strategist for Mitsunari. Even though Yoshitsugu suspected the betrayal and was prepared for the attack, his unit was overrun, and he committed seppuku.

After Kobayakawa Hideaki’s betrayal, the battle suddenly turned from being a Western Army victory to an Eastern Army victory. Some of the other wavering generals in the Western Army finally got the courage and began attacking their former allies. Other generals began to retreat, one being the commander himself, Ishida Mitsunari. By two o’clock on October 21, 1600, the country’s fate had been sealed: Tokugawa Ieyasu finally had Japan in the palm of his hand.

Aftermath

The battle only lasted six hours and resulted in a victory for the Eastern Army. Tokugawa Ieyasu would not totally assume power until 1603, when he became shōgun of the country, establishing the Tokugawa Shogunate and ushered in a new era of Japanese history. As for Ishida Mitsunari’s fate, he would be captured not long after the battle. He would be executed in Kyōto on November 6, 1600. Many other generals of the Western Army who survived the battle, faced many different fates. Some were executed, like Mitsunari. Others surrendered unconditionally, like Noae Kanetsugu. Ultimately, he saved the Uesugi clan by doing so. Others, like Sanada Yukimura, were sent into exile. The battlefield has been turned into a national park of sorts today, and stands as a reminder of one of the bloodiest battles in Japanese history.