Battle of Sekigahara

Locale A small post station in Mino Province (now southwest of Gifu), Japan

Date October 21, 1600

The Battle of Sekigahara marked the last major conflict in the Japanese wars of unification. Tokugawa Ieyasu defeated an alliance of rival warlords and assumed uncontested control of Japan. As shogun, he outlawed private armies to ensure domestic peace and tranquillity, and he imposed a policy of enforced isolation that lasted until American warships opened Japan to international trade in 1846.

Key Figures

• Kobayakawa Hideaki (1577-1602), military commander

Summary of Event

In Japanese society, local warlords known as daimyo owned and administered districts or provinces. Although in theory the emperor was supreme, only the daimyo could raise taxes, so during Japan’s medieval era most emperors were weak and held only titular power. Real political power rested with the daimyo, and throughout the era a number of highly influential daimyo fought one another to expand their holdings or to gain preeminence. The highest rank a daimyo could attain was that of shogun. Although the literal translation of the Japanese word shōgun is “barbarian-quelling generalissimo,” in reality, the position was that of military dictator.

In 1185, the first shogunate, or administration of a shogun, was established. For the next five centuries numerous daimyo struggled for supremacy. The conflicts of the sixteenth century were particularly vigorous and bloody. Japanese historians refer to this period as Sengoku Jidai, the Age of the Country at War, or the Warring States period. During the later years of this century, one particularly successful general was Toyotomi Hideyoshi. By 1585, Hideyoshi had defeated rivals and administered the nation for the emperor as kampaku (chancellor of the emperor) through his control over a coalition of dependant daimyo. Hideyoshi was the first leader to unify Japan under one man’s authority.

When Hideyoshi died in 1598, however, his six-year-old son was too young to come to power, so the coalition of subordinate daimyo dissolved into two rival alliances. The primary leaders of these alliances had been important subordinates of Hideyoshi. Ishida Mitsunari had been a civil administrator more than a general, and by virtue of his schemes and political manipulations he came to command what became known as the Western Army. Many of the daimyo in the Western Army were less inclined to support Mitsunari than they were eager to oppose Tokugawa Ieyasu. Ieyasu had been one of Hideyoshi’s generals and was also the richest daimyo in Japan. His wealth made him both the target of much resentment and a natural leader. Many assumed that when Hideyoshi died, Ieyasu would be his successor by default. The forces of the daimyo that supported Ieyasu soon came to be called the Eastern Army.

In 1600, Ieyasu’s leading opponents attempted to isolate him politically. In response, Ieyasu mobilized his forces and began the decisive campaign. Mitsunari’s strategy was to divert Ieyasu with attacks on Ieyasu’s eastern lands. With Ieyasu thus distracted, Mitsunari’s Western Army would concentrate and overwhelm Ieyasu. On the day of battle, the Western Army numbered about 80,000 soldiers. In response to Mitsunari’s gambit, Ieyasu diverted some of his troops to screen the eastern attack while he rapidly moved approximately 88,000 men to confront Mitsunari’s Western Army. Surprised, Mitsunari retreated to the small crossroad village named Sekigahara. There he planned to ambush Ieyasu. Mitsunari deployed his forces in a long, L-shaped array. About 34,000 troops were deployed in the lower bar of the L in blocking positions athwart the road that ran through Sekigahara. The shaft of the L lay along the sides of two mountains, Matsuo and Nangu. Upon and behind these heights, Mitsunari stationed nearly 48,000 soldiers. These troops were held far enough above the valley floor to be screened from view. Mitsunari’s plan was that Ieyasu’s forces would attack along the valley floor without seeing these forces, and at the opportune moment Mitsunari would order the contingents on Matsuo and Nangu to charge down the mountains to surround and destroy Ieyasu’s army.

What Mitsunari did not realize was that his own arrogant personality and lack of diplomatic skill had alienated many of the ostensibly anti-Ieyasu daimyo. Mitsunari had, for example, relegated his most experienced battlefield commander to a virtual exile in Ōsaka, where the man was locked into a largely ceremonial position. Thus Mitsunari removed a rival, while also depriving the Western Army of its most talented battle leader. Ieyasu benefited from such slights, and before the battle began, he secretly convinced many of the disaffected daimyo in the Western Army to defect. These daimyo agreed to not switch sides until battle was joined.

The battle began early on the morning of October 21, 1600. The weather was foul, with a heavy fog masking Ieyasu’s approach. Around 8:00 a.m. the fog burned off, and Ieyasu’s men attacked headlong into Mitsunari’s position. The fighting was heavy and bitter throughout the morning. Both sides fielded large numbers of harquebusiers, but the mist and light rain dampened the gunpowder and minimized the impact of fire. A hastily erected fence acted as a shield for some of Mitsunari’s gunners and helped to anchor his position. Throughout the morning, Ieyasu’s men attacked a force that comprised less than half of the Western Army, much as Mitsunari had planned. Although Ieyasu’s forces were more numerous at the point of contact, Mitsunari’s defensive position and the valor of his men allowed them to resist effectively.

Having held Ieyasu’s men in place, Mitsunari ordered the forces from the two mountainsides to move out from cover and attack. The crucial force for this attack was the contingent led by Kobayakawa Hideaki, as his force was the pivot connecting Mitsunari’s contingent with the other forces deployed along the length of Mount Nangu. Because Hideaki was between these forces and Mitsunari, the other daimyo deployed along the mountain could not see the signal to attack. Hideaki had secretly agreed to aid Ieyasu, and at about noon, he ordered his men to attack Mitsunari’s position. Mitsunari loyalists arrayed behind Hideaki were unaware of Mitsunari’s commands to attack and were thus thrown into confusion by Hideaki’s attack on Mitsunari.

Mitsunari’s men, who had been holding off Ieyasu’s forces since dawn, were suddenly confronted on two sides. Exhausted by the long morning’s fight and demoralized by the treacherous attack, Mitsunari’s forces began to disintegrate. Hideaki’s contingent was not the only group of turncoats. Five other daimyo switched sides during the battle, bringing about 23,000 men to Ieyasu’s assistance. Once Mitsunari saw what was happening, he abandoned his forces and fled from the battlefield.

Mitsunari’s plan had failed because of treachery, but his rapid departure from the battle rendered impossible any rally of the remaining loyalist contingents. Ieyasu’s victory shattered the Western Army, and many of its daimyo rapidly shifted their loyalties to him. Mitsunari was ultimately captured and executed. Although Ieyasu would require another sixteen years to secure undisputed rule of Japan, the victory at Sekigahara removed the only effective and unified force that could have opposed his campaign to be named shogun.

Significance

Ieyasu’s victory at Sekigahara made possible his rise to the position of shogun. As the military dictator of Japan, he was able to carry through a number of reforms that had begun under Hideyoshi. These reforms included destroying privately owned fortifications, outlawing the ownership of arms by anyone other than samurai, and ossifying the social classes. These laws essentially ended the private armies of the daimyo and turned the samurai class into government administrators.

Ieyasu also outlawed foreign trade and, as a result, isolated Japan from developments elsewhere. These reforms profoundly changed Japanese life. In addition, Ieyasu’s success allowed him to found a dynasty of shoguns that came to be known as the Tokugawa shogunate. Ieyasu’s descendants would rule Japan until 1868, a future that would have been impossible without the clear-cut victory at Sekigahara.

Bibliography

Bryant, Anthony. Sekigahara, 1600: The Final Struggle for Power. London: Osprey Books, 1996. This is an excellent study of the battle and the political maneuverings that created the two alliances.

Turnbull, Stephen. The Samurai: A Military History. New York: Macmillan, 1977. Turnbull is a tremendously well-respected scholar of the samurai. This book is an excellent study of the development of the samurai and their ethos. It is a particularly valuable work for its battle studies.

Turnbull, Stephen. Samurai: The World of the Warrior. London: Osprey Books, 2003. An excellent and accessible book, this work is suitable for a wide variety of ages.

Turnbull, Stephen. Samurai Warfare. London: Arms and Armour Press, 1996. Another very fine effort by Turnbull, this work is an excellent overview of the nuts and bolts of how samurai forces were organized, equipped, and led, and how they fought.