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An Overview of the Sengoku Jidai

Map of Sengoku Japan

The Sengoku Jidai, is also known as the “Warring States Period” to English scholars, which is actually an almost literal translation. While English Japanese historians can agree on the name of the era, for some reason, they cannot agree on the years. Many start the beginnings of the Sengoku Jidai with the Ōnin War (1467-1477). Some start with the birth of Oda Nobunaga in 1534. Starting there, however, skips over a large part of history that should be considered part of the Sengoku Jidai, for the country was thrown into civil war before then. When it actually ends has also not been agreed upon by historians. There are three distinct events that historians label as the end of the Sengoku Jidai: the Siege of Odawara Castle in 1590, The Battle of Sekigahara in 1600, and the Summer Siege of Ōsaka Castle in 1615. For this website, we will be looking at its beginnings in 1467 and ending with the final battle in 1615.

The Ōnin War

The Ōnin War (1467-1477), is seen as the catalyst for the Sengoku Jidai. The war broke out over a succession dispute within the Ashikaga Shogunate. The shōgun of the time, Ashikaga Yoshimasa, wanted to retire from the office, but he had no heir to take over. In 1464, Yoshimasa began trying to persuade his brother, Ashikaga Yoshimi, to leave his life as a monk and become the new shōgun. Things become complicated when Yoshimasa’s wife, Tomiko, gave birth to a son, named Yoshihisa. The issue of succession was brought to the attention of Hosokawa Katsumoto and Yamana Sōzen, both leaders of clans who worked under the shōgun. They stood on opposing sides on who should take over as the new shōgun: Hosokawa sided with Yoshimasa and Yoshimi, while Yamana sided with Tomiko and the newborn, Yoshihisa. Tensions began to rise and eventually led to the Hosokawa and Yamana clans fighting within the city of Kyōto in 1467, thus beginning the Ōnin War. The war ended with no clear victors. Both Hosokawa Katsumoto and Yamana Sōzen both died in 1473, just four years before the end of the war. By 1477, the city of Kyōto laid in ruins. The Ashikaga Shogunate lost considerable power after the war, serving as puppets to the Hosokawa who managed to gain control of the shogunate. The divide that the Ōnin War caused spread outside of Kyōto, which resulting in the Sengoku Jidai.

The Age Before the Three Unifiers

After the Ōnin War, we see a divided Japan. Clans that were once prominent ages ago collapsed with the rise of others. By the time the Three Unifiers arrive on the scene, only twenty of Japan’s most powerful clans, those who have been powerful for many generations, were left. This age before the most famous names of the era was plagued by war and conquest. The takeover of the Chūgoku region by Mōri Motonari and some of the battles of Kawanakajima took place during this age.

Map of Japanese clans in 1545

Map of Clans and Their Territories in 1545.

The Three Unifiers

The Three Unifiers really played a part in the last fifty-five years of the Sengoku Jidai. These men were Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu. These men were quite different from one another, which can be seen in a poem that Japanese schoolchildren have to learn. The Three Unifiers were asked what they would do with a bird that would not sing. Nobunaga said that he would kill it, Hideyoshi said that he would make it sing, and Ieyasu said that he would wait for it to sing. These would be men who would lay the foundations for unification.

The first Unifier was Oda Nobunaga. He made his first move towards unification at the Battle of Okehazama in 1560. From there, he began to expand his territory and helped restore and destroy the Ashikaga Shogunate. He changed the dynamics of Japanese warfare at the Battle of Nagashino in 1575. Nobunaga was close to conquering Japan, however, he committed seppuku when one of his retainers, Akechi Mitsuhide, turned traitor and attacked Nobunaga at the Honnō-ji Temple in Kyōto on the night of June 21, 1582.

Toyotomi Hideyoshi was the next Unifier to try to take over Japan. He would avenge Nobunaga’s death by killing Akechi Mitsuhide at the Battle of Yamazaki. He would wind up taking over the remains of Nobunaga’s land and through many campaigns he managed to conquer Japan after the Siege of Odawara Castle in 1590. Hideyoshi was actually the one to unify the country, however, he is not really acknowledged as such because he could not take the title of shōgun due to his peasant upbringing. He had to settle for the title of kampaku, which was similar to the role of prime minister. While he did not carry the title of shōgun, Hideyoshi still ran the country like he was. He made major changes to the Japanese military and social class, and even tried to extend his reach beyond the shores of Japan, by trying to conquer China by going through Korea. This resulted into two Korean Campaigns, one in 1592 and another in 1597.

Toyotomi Hideyoshi passed away in September 1598, leaving behind his five-year old son, Hideyori and a group of generals and administrators to run the country. Problems arose when the third Unifier, Tokugawa Ieyasu, began taking steps to completely take over the Toyotomi regime. Ishida Mitsuanri, a man loyal to the Toyotomi, made attempts to stop Ieyasu. This caused a divide within the Toyotomi clan: the Western Army under Mitsunari and the Eastern Army under Ieyasu. After a year of small skirmishes between the two sides, they would finally meet at Sekigahara on October 21, 1600. Ieyasu defeated Mitsunari and he became shōgun in 1603.

The Final Years

Tokugawa Ieyasu stepped down as shōgun in 1605, allowing for his son, Tokugawa Hidetada, to take over as shōgun. The Tokugawa Period, also known as the Edo Period, was underway. There was still a problem, for Toyotomi Hideyori was gathering support from many rōnin from across the country who came to stay at his father’s castle at  Ōsaka. This posed a threat to the newly established shogunate, so Ieaysu took to the battlefield one last time and laid siege to  Ōsaka Castle in the winter of 1614. The siege did not end until the summer of 1615, with Ōsaka Castle up in flames and Hideyori dead. The Sengoku Jidai was officially over.