The Battle of Sekigahara – 関ケ原の戦い

October 21, 1600… Fog covered the battlefied and tension ruled over the soldiers on both sides… The fate of the Japanese Empire was hanging in the balance as the country stood in need of a new leader to unite the people. Two major candidates emerged and were determined to take over. But one final battle was awaiting… The Battle of Sekigahara was perhaps one of, if not the most decisive battle in the history of Japan and sealed the country’s fate for the next 250 years. But what happened exactly? Who were these candidates and how did this single battle forge history as it did?

the battle of sekigahara

Main Characters

When discussing any event in history, especially one relating to the political sphere, it is always difficult to get a grasp of everything that’s going on and really understand who’s who and who does what. So first, I think a formal introduction to the main characters of this story is in order.

Toyotomi Hideyoshi – 豊臣秀吉 (1537 – 1598)


Toyotomi Hideyoshi was a Daimyō who rose through the ranks and became the de facto ruler of Japan and acted as the second Great Unifier of Japan after Oda Nobunaga. He launched a series of campaigns against Korea in 1592 spanning over 6 years which in the end damaged his prestige. His death in 1598 entailed conflicts as to who should succeed him, which led to the Battle of Sekigahara.

Ishida Mitsunari – 石田三成 (1559 – 1600)


Ishida Mitsunari was a military commander and Daimyō who served under Toyotomi Hideyoshi as one of the Go-Bugyō, which is to say as one of his top administrators. He was one of the two candidates for power after Hideyoshi’s death and he led the western army during the Battle of Sekigahara.

Tokugawa Ieyasu – 徳川家康 (1543 – 1616)


Tokugawa Ieyasu was the third Great Unifier of Japan. He was first a Daimyō serving under Oda Nobunaga as general and vassal before he served under Toyotomi Hideyoshi after Nobunaga’s death. He then became one of the most powerful lords of the country and acted in 1598 as the most prominent lord on the Council of the Five Elders of the Toyotomi government. After Hideyoshi’s death, Ieyasu became the other major candidate for power, leading the eastern army during the Battle of Sekigahara. He eventually became Shōgun and led the country toward a new era.

Kobayakawa Hideaki – 小早川秀秋 (1582 – 1602)


Kobayakawa Hideaki was a young Daimyō who served under Toyotomi Hideyoshi notably as a military commander during the invasion of Korea. Despite his young age and lack of experience, he had an immense impact on the outcome of the Battle of Sekigahara and on the history of Japan.

Political Situation

Let’s go back to a time when the Empire of Japan was ruled by Samurai. This was a time when the most valuable currency was none other than a small grain we all know and love: rice. Rice fed the population, therefore, those with the most land to produce rice held the highest ranks in society. Rice dictated the everyday lives of the people. This led to lords being in possession of very valuable lands and having much power. This was the case of what we call Daimyō (大名). These feudal lords held the vast majority of the land throughout the Empire and wielded much power and influence. Said power was apparent through the many castles that each lord possessed.

This was also a time when near constant civil wars laid waste to the country. These skirmishes were a result of the amount of power that emanated from local lords: conflicts and treachery were common sights in 15th to 16th century Japan. This era was known as the Sengoku period (戦国時代, lit. ‘Age of Warring States’).

map of japan 1590
Map of Japan’s main island in 1590
Yellow = Toyotomi territory
Light Red = Tokugawa territory

At that point, the Emperor didn’t hold much real power, he rather acted as a spiritual leader for the country than he did a political or military commander. That role belonged to the de facto ruler of the Empire: the Shōgun (将軍), whose influence was very much balanced by the local powers of Daimyō. The country’s governance therefore resulted in a fragile equilibrium between the power of the Shōgun and the local influences of Daimyō.

Enter main character number one: Toyotomi Hideyoshi. Before he came to power, there was another ruler called Oda Nobunaga (織田信長, 1534 – 1582) who initiated a war of unification by conquering land on Japan’s main island: he was known as the first Great Unifier of Japan. Hideyoshi succeeded Nobunaga in power and pursued the war for unification, deed for which he is known today as the second Great Unifier of Japan.

After having achieved a degree of unity in a country that hadn’t seen anything of the like for ages, Hideyoshi decided to invade Korea. The first campaign launched in 1592 was initially met with success. However, after a short truce in 1596, a second invasion in 1597 proved to be a immense failure deeply weakening the Toyotomi rule and those in the government.

siege of dongnae during japanese invasion of korea in 1592
Siege of Dongnae during the Japanese invasion of Korea in 1592

This is where the other main characters come in. First: Kobayakawa Hideaki. Yet young and inexperienced, he was appointed to lead troops during the second invasion of Korea. The defeat that ensued resulted in the Toyotomi government blaming and humiliating Hideaki upon his return to Japan. Among those blaming and severly humiliating Hideaki was Ishida Mitsunari, one of Hideyoshi’s top administrators. This proved to be a turning point for what was to follow as it induced resentment on Hideaki’s part toward the government and Mitsunari, which would later lead to Mitsunari’s demise.

There was one man however whose power and influence did not suffer as much from the defeat in Korea. This man was none other than future Shōgun: Tokugawa Ieyasu. He was by far the most highly regarded military commander of the country and his seniority was rivaled by no other. While most within the Toyotomi government agreed to blame Hideaki for what happened in Korea, Ieyasu seemed to defend him, a strategy that later paid off.

In 1598, Hideyoshi’s health was failing and he didn’t have much time left. However, there was one problem regarding his succession: his last living heir (Toyotomi Hideyori) was only five years old. To ensure that his rule would last after his lifetime, Hideyoshi appointed the Council of the Five Elders, of which Ieyasu was a part, that would be in charge of ruling on his son’s behalf until he came of age. The fact that Hideyoshi didn’t have an assertive heir capable of ruling after him would be the cause of the conflicts leading to the Battle of Sekigahara.

toyotomi hideyori: hideyoshi's son
Hideyoshi’s son: Toyotomi Hideyori (豊臣秀頼)

The Divide

On September 18th, 1598 Toyotomi Hideyoshi’s death would leave the country in the hands of his government until his son could himself rule. Unfortunately for the young Toyotomi Hideyori, oblivious to the political schemes taking place around him, certain members of the current government had other plans.

It was no secret that Ieyasu and Mitsunari had never had a thing for each other. Both of them were ambitious men and both had power in their sights. The picture was quickly being drawn; two prominent figures of the government were going for the helm, but only one of them could ultimately have access to it. The lords of the country were now faced with a troubling choice: should they remain loyal to the current government and follow Mitsunari? or should they join the Tokugawa rebellion?

Following this pattern, two feuding factions rapidly arose. On one side were the Toyotomi clan loyalists and western lords rallied behind Mitsunari; and on the other were eastern lords and sympathizers of Ieyasu. West vs. East.

One interesting and very important thing to note as well is the fact that the young Kobayakawa Hideaki, despite having been humiliated by the Toyotomi government and Mitsunari himself, decided to remain at his side when faced with choosing between him and Ieyasu.

Tensions grew between the two factions as both sides kept recruiting lords to fight alongside them. Mitsunari especially feared Ieyasu’s overall unequalled influence which allowed him to recruit partisans with ease. This encouraged Mitsunari to do so as well and tensions kept rising until open hostilies finally appeared.

Preliminary Battles

Although what truly sealed the fate of the country was the final battle that occurred at Sekigahara, a number of less substantial (though not unimportant) battles preceded it. It was a succession of military operations (often sieges of castles) throughout the Kansai region that led, after several weeks, to the two armies finally meeting face to face and putting an end to this whole dispute.

As one might have predicted, Mitsunari and Ieyasu were not the only Daimyō to see the opportunities lying in the collapse of the Toyotomi government. A certain Uesugi Kagekatsu (上杉景勝) started building up an army and erecting fortresses toward the east. Needless to say that such actions did not particularly please Ieyasu who viewed him as dangerous and decided to attack him with troops he had positioned in Osaka.

osaka castle
Osaka Castle

However, once said troops had departed from Osaka Castle where they were stationed, they (obviously) couldn’t defend the castle anymore. Mitsunari took advantage of that and launched an attack on Osaka Castle once Ieyasu’s army had vacated the area. With Osaka Castle newly captured, Mitsunari’s army proceeded to march east.

When Ieyasu got the news of what was going on, he departed from Edo with all of his forces and those of his allies and started marching toward the western army, toward Mitsunari.

After a few weeks of marching and castle sieges, the two armies finally met. Mitsunari’s corps was holding a defensive position in a secluded valley at Sekigahara, in current Gifu prefecture when Ieyasu’s men caught up on October 20, 1600.

The final battle was finally awaiting. The two armies had never been closer. However, there was one army who seemed to have an advantage: the western army outnumbered the eastern one. Although it is hard to pinpoint the exact number of men making up each corps (different sources seem to give different numbers), one thing seems to be commonly accepted: Mitsunari’s army outnumbered Ieyasu’s with around 80,000 ~ 100,000 men over Ieyasu’s 70,000+ men.

With the tactical advantage provided by the terrain and the amount of men Mitsunari had at his side, victory seemed guaranteed. But Ieyasu had other plans…

The Tokugawa Scheme

Tokugawa Ieyasu was a very experimented commander and knew very well the inner workings of such crucial conflicts. Before the two armies met, Ieyasu had been colluding with commanders of the western army to bring them to his side. And although a lot of the lords did not like Ieyasu, few of them actually wanted to fight a battle against him seeing as his military strength rivaled that of Toyotomi Hideyoshi.

A crucial but rather uncertain alliance would lead Ieyasu to victory: that with Kobayakawa Hideaki, the young Daimyō previously humiliated by Mitsunari. A week before the final battle, Ieyasu received a letter from Hideaki, informing him that, come the decisive battle, the young Daimyō would betray Mitsunari and fight alongside him. But could Ieyasu trust the message he had received? He couldn’t be certain. Were those Hideaki’s real intentions? Or was it a trap orchestrated by Mitsunari to get the upper hand? There was only one way to be sure.

The Battle of Sekigahara

October 21, 1600. Rain had fallen down all night long… Fog now covered the battlefield. Tension ruled the atmosphere. This was the moment that was going to end this whole conflict. Weeks of hostilies terminated in a single battle. This moment was going to shape history and set the country on a whole new path.

Mitsunari had positioned his troops on higher ground and was waiting for Ieyasu to make the first move. His plan was to wait for Ieyasu’s troops to charge, at which point he would counterattack and flank the rebel army with Hideaki’s men. He was also waiting for troops led by Daimyō Mōri Terumoto (毛利輝元), who had captured Osaka Castle before the battle and who remained there. Unfortunately for Mitsunari, Terumoto decided not to fight the battle against Ieyasu and his troops would never arrive.

Ieyasu’s army reached Sekigahara worn out, and took position in the heart of the valley. Doubts regarding Hideaki’s true intentions still weighed on Ieyasu’s mind, he couldn’t risk falling into a trap.

The time had come. Both armies were in position, ready to put an end to this; all Ieyasu had to do was give the order. And he did.

battle of sekigahara

His army, despite being outnumbered, charged Mitsunari’s and the fight began. Arquebuses were fired, swords clanged and the valley became a battleground. Through the fog, soldiers roared and fought valiantly, putting their all into the fight. Despite relentless sword crossing, the fight was stalling. No army managed to get the better of the other.

But at some point, despite the tireless fighting, Tokugawa’s army started to weaken and left their flank exposed. This was what Mitsunari had been waiting for. Realizing this, he ordered Kobayakawa Hideaki and his 15,000 men to flank Ieyasu’s army and cash in the victory. But Hideaki didn’t budge. Even though he told Ieyasu that he would betray Mitsunari and switch sides, seeing how the eastern army’s inital charge hadn’t exactly paid off and how it was slowly weakening made Hideaki hesitate. Was he really going to go through with it? He withheld the order to attack Ieyasu. This young Daimyō held the fate of the Japanese Empire in his own hands. What he was going to do would shape history.

Ieyasu had spotted Hideaki’s troops and was finally going to know his true intentions, the doubt could not last any longer. But Hideaki wasn’t moving, still undecided. Ieyasu wasn’t one to wait around and let others become masters of his own fate. Whether Hideaki was going to join Ieyasu, or whether he was going to fight against him, he had to make a choice. Neutrality was not an option. And there was only one way for Ieyasu to know what Hideaki had in mind. In the midst of battle, through the roars and fog of war, Ieyasu ordered his men to fire and attack Hideaki and his troops. If Hideaki couldn’t choose, Ieyasu was going to make him.

Ieyasu’s risky but assertive strategy paid off. The message was loud and clear and Hideaki had heard it. When the young Daimyō saw the eastern army’s offensive toward him, he ordered his men to change direction and charge Mitsunari’s army. He had given his verdict: he was a member of the eastern army. And with this, Hideaki had decided of the future of Japan.

map of the battle
Map of the battle
Red = eastern army / Blue = western army
Far right: Tokugawa Ieyasu
Bottom left: Kobayakawa Hideaki
Top left: Ishida Mitsunari

Hideaki’s betrayal resulted in a cascade of commanders seeing the tide turn and themselves defecting, which consequently resulted in the collapse of the western army. The now strengthened eastern forces overwhelmed the western troops. There was nothing Mitsunari could do to stop what was coming. In a matter of hours, the western army had been bested by the eastern army and had lost the battle. Ishida Mitsunari had been defeated and Tokugawa Ieyasu was victorious.


The Battle of Sekigahara was by far the bloodiest and deadliest of Medieval Japan with 30,000 casualties after a 6 hour fight. After the battle, Ishida Mitsunari was captured by the eastern army and beheaded, leaving only one candidate for power: Tokugawa Ieyasu, who become the undisputed ruler of Japan. In 1603, he was appointed Shōgun by the Emperor himself. From then on Ieyasu established a new state and strove to protect the country from civil war; he became the third Great Unifier of Japan.

To limit the power of local lords he ordered the destruction of many castles throughout the country, and to better control the lords themselves, he ordered them to reside regularly in the new capital: Edo, which would later be renamed to Tokyo in 1868.

Ieyasu established much stricter border rules: foreign trade was severly limited and generally had to undergo his direct approval. All foreigners, except Chinese and Dutch, were prohibited from entering the country. Japanese people themselves were not allowed to leave the country anymore. At this point, Japan turns inward and enters a long period of isolationism which it will have to be forced out of two centuries later.

Ieyasu also banned Christianity. More than 300,000 Japanese people were Christians at the time and those who wouldn’t comply with this newfound ban were persecuted.

Policies of urbanization further bettered the economy of the country which would see substantial growth along with agricultural development.

After the Battle of Sekigahara, Tokugawa Ieyasu led the country toward a completely new era: the Edo period. Despite having taken the power illegitimately and by force, Ieyasu had brought an end to the civil wars that ravaged the country and offered more than 250 years of peace and development to the country. This peaceful and stable situation would allow the population to explore and develop new cultural aspects through arts such as Ukiyo-e or different fields that were less accessible.

ukiyoe of edo
Ukiyo-e of Edo

This battle proved to be a turning point in history and has shaped the path that Japan would follow for more than 250 years.


“Butterfly Effect – Season 1”, produced by Mad Films (2016) (Sekigahara episode)

Leave a Reply

Your email address will not be published. Required fields are marked *

%d bloggers like this: