Despite its small size, Japan has been at war throughout its history. The number of foreign invasions is relatively small, and the internal culture is homogeneous, so the war is inherently internal and feudal. These conflicts lasted for centuries and many decisive battles were fought. But none of them are as important as the Battle of Sekigahara. It was the largest of its time, and it determined Japan's fate for the next 250 years.
In the late 15th century, Japan entered the Sengoku period. The authority of the emperor has been a formality for centuries, and now, the real ruler, the shogun from the Ashikaga clan, has also lost control. Small regional conflicts and deteriorating economic situations have become emblematic of this era.
In 1559, Oda Nobunaga consolidated his hometown of Owari. A year later, Oda Nobunaga repelled an attack by the Imagawa clan. In 1567, Saito was defeated and their lands were conquered. Ashikaga Yoshiaki, the heir to the shogunate, was exiled from the capital Kyoto and sought Nobunaga's help.
In 1568, Oda Nobunaga defeated the rebels and pushed Yoshiaki back to power. He continued to fight his neighbors, capturing Ise Nation in 1569 and Sakai, then one of Japan's largest cities. Oda Nobunaga was eager for more power so in the same year that he sent a letter with 16 demands to the shogunate in an attempt to limit the shogun's power. Although Ashikaga initially agreed, he began to ally with Nobunaga's enemies: Asai, Asakura, and the Takeda clan. Oda Nobunaga's conflict with these enemies began in 1570, and despite the help of the Tokugawa family, Oda Nobunaga lost the first battle.
In 1573, his ally Tokugawa Ieyasu lost the Battle of Mikunihara. Thankfully, Takeda's leader, Takeda Shingen, died of illness in the same year, which allowed Nobunaga to defeat Asai and Asakura. The shogun was again exiled, and his second attempt to organize an alliance in 1576 failed.
By 1582, much of central Japan was under Nobunaga's control. Oda Nobunaga used trade with Portuguese merchants to gain an advantage. The gunpowder weapons bought from them strengthened his military strength. Arquebusiers began to replace archers in the Japanese army. Oda Nobunaga also allowed Christianity to be preached in Japan and wore European clothing. But his cruelty to Buddhist temples and ruthless pragmatism to his subordinates eventually led to his destruction.
In 1582, his general Mitsuhide Rebelled against Nobunaga. Surrounded by Kyoto, Oda Nobunaga had no choice but to commit suicide by caesarean section. Oda Nobunaga's two main allies (Ieyasu), Tokugawa Ieyasu and Toyotomi Hideyoshi, began to compete for his place. However, it was Toyotomi Hideyoshi who defeated Mitsuhide at the Battle of Tennozan.
Because he was not of noble birth and could not become a shogun, in 1585 he was appointed regent Sekibai. By 1590, he had defeated the Hojo clan, thus unifying Japan under his power. Japan has set its sights on overseas. Toyotomi Hideyoshi tried to invade Korea twice. Despite some initial successes, these invasions ultimately failed.
Domestically, Toyotomi Hideyoshi was eager to keep power firmly in the hands of his family. Initially, his nephew Hideji was declared heir. But in 1593, a new son, Toyotomi Hideyoshi, was born and became heir apparent.
In 1598, Hideyoshi fell ill. He immediately appointed Japan's most powerful feudal lord as the head of his son. The five elders ruled with the five priests until Toyotomi Hideyoshi came of age. In the same year, Toyotomi Hideyoshi died. Almost immediately, they began to organize the conspiracy. Tokugawa Ieyasu was the most powerful of these elders, and he repeatedly married other clans. At the same time, one of them, Ishida Sansei, began plotting to weaken Ieyasu's position. Ishida tried to assassinate his opponent, but the killer failed.
The situation was exacerbated by the death of another Maeda Toshiya in 1599, and Tokugawa Ieyasu took control of Osaka Castle. Uesugi Keisetsu began to build a new fortress on the border with Tokugawa. When the envoys sent out by Tokugawa Ieyasu were insulted, they left Osaka in July 1560 with his army to punish Keisatsu.
Eight senior priests led by Ishida Sansei took advantage of his absence and issued an ultimatum to Tokugawa Ieyasu in August, making war inevitable. Ishida and his supporters declared their loyalty to Toyotomi Hideyoshi and formed what is now known as the "Western Army". Tokugawa Ieyasu and his allies are now known as the "Eastern Army". The leaders of the Western Army hoped that Tokugawa Ieyasu would continue to be busy with the war with Keisatsu. His plan was to take the main road connecting Edo and Kyoto.
Fushimi's castle blocked Ishida's way and was besieged on 27 August. The 2,000-strong defenders resisted Ishida's 30,000-strong army for 10 days. The Western Army lost 3,000 soldiers, but more importantly, they lost valuable time. After a slow advance, Ishida and his men arrived in Ogaki in October.
Maori Huiyuan began to move with 30,000 warriors. Tokugawa Ieyasu and his soldiers arrived in Akasaka on October 20, where he set up a camp on a hill called Okayama. There were about 80,000 fighters on both sides. Sansei decided to order the withdrawal of their troops to Sekigahara, where, according to him, they would have a tactical advantage.
The battle took place in Sekigahara on October 21, 1600. At 4:30 a.m., the Western Army lined up and entered the battle position. Tokugawa Ieyasu also ordered his army to deploy. A thick fog shrouded the valley, so visibility was reduced to a few meters, and it was difficult for the troops to identify the enemy. At 8 a.m., the fog cleared. After a while, the confrontation began. It is not entirely clear which side the attack began on, but it appears that a small cavalry unit of the Eastern Army was attacked first. The Initial Attack of the Western Army was so surprising and violent that they reached the front of the Shimazu clan.
On the other side of the battlefield, the attack threatened Yoshimitsu Otani's position, but this attack was contained. Nearly 20,000 soldiers of the Eastern Army pointed directly at ishida's left flank. A temporary defensive circle was created to prevent them from rendezvousing with 30% of the troops, and this attack was blocked by flank troops in the area.
Tokugawa Ieyasu sent more troops into the area, but Ishida Mitsunari's soldiers, with the support of the Honjin, managed to fend off these attacks. As ishida's center was somewhat weakened, a group of arquebusiers were sent out and managed to shoot. However, the leaders of the Western armies moved their own musket troops into the area, and Tokugawa Ieyasu's musket troops were pushed back.
Ishida's arquebusiers tried to counterattack, but their flanks were threatened and they were forced to retreat back to their positions. The battle is now in a stalemate phase. However, more and more troops of the Eastern Army began to join the fighting on the front line. Seeing this, Ishida ordered Shimazu to join the battle from the flanks, but they refused the order. On the right, Hideaki Hayakawa was also ordered to support honjin. Unfortunately for Ishida, Hideaki Hayakawa betrayed him and promised loyalty to Tokugawa Ieyasu. Hideaki Kohayakawa's forces joined the Eastern Army, and together they began to storm the center of Ishida Sansei.
The leaders of the Western Army tried to retreat. Ishida also had a trump card in his hand as his troops, including those from the Maori, Nagamasa, and Yoshikawa clans, who had not been wounded. When Ishida's home and left flank retreated, the enemy was drawn in, and a single attack could change the course of the battle. However, Yoshikawa, who was in the front, refused to attack and did not allow the Maori army or the Nagamasa Ibu army to join the battle. Eventually, the entire force withdrew from the battlefield.
Ishida's remaining forces were soon surrounded and massacred. The Western Army lost as many as 40,000 soldiers, while Tokugawa Ieyasu lost about 5,000 men, and most Western Commanders were killed in battle or executed after the war.
Victory in the Sekigahara War allowed Tokugawa Ieyasu to seize control of the country and eventually establish the Tokugawa shogunate. The Warring States period ended. The new relative peace will last for 250 years.