A History of Japan: From Mythology to Nationhood/The Warring States Period

The Sengoku period (戦国時代 Sengoku Jidai) or Warring States period in Japanese history was a time of social upheaval, political intrigue, and nearly constant military conflict that lasted roughly from the middle of the 15th century to the beginning of the 17th century. The name "Sengoku" was adopted by Japanese historians in reference to the Warring States period in Chinese history which preceded the unification of China. Likewise, the Sengoku period in Japan would eventually lead to the unification of political power under the Tokugawa shogunate. Although the Ashikaga shogunate had retained the structure of the Kamakura bakufu and instituted a warrior government based on the same social economic rights and obligations established by the Hōjō with the Jōei Code in 1232, it failed to win the loyalty of many daimyo, especially those whose domains were far from Kyoto. As trade with China grew, the economy developed, and the use of money became widespread as markets and commercial cities appeared. This, combined with developments in agriculture and small-scale trading, led to the desire for greater local autonomy throughout all levels of the social hierarchy. As early as the beginning of the 15th century, suffering and misery caused by natural disasters such as earthquakes and famines often served to trigger armed uprisings by farmers weary of debt and taxes. The Ōnin War (1467–1477), a conflict rooted in economic distress and brought on by a dispute over shogunal succession, is generally regarded as the onset of the Sengoku period. The "eastern" army of the Hosokawa family and its allies clashed with the "western" army of the Yamana, and fighting in and around Kyoto lasted for nearly 11 years, after which it spread to outlying provinces.

Gekokujō
The upheaval resulted in the further weakening of central authority, and throughout Japan regional lords, or daimyo, rose to fill the vacuum. In the course of this power shift, well established clans such as the Takeda and the Imagawa, who had ruled under the authority of both the Kamakura and Muromachi bakufu, were able to expand their spheres of influence. There were many, however, whose positions eroded and were eventually usurped by more capable underlings. This phenomenon of social meritocracy, in which capable subordinates rejected the status quo and forcefully overthrew an emaciated aristocracy became known as gekokujō (下克上?), which literally means "the underling conquers the overlord." One of the earliest instances of this phenomenon was Hōjō Sōun, who rose from relatively humble origins and eventually seized power in Izu province in 1493. Building on the accomplishments of Sōun, the Late Hōjō clan remained a major power in the Kantō region until its subjugation by Toyotomi Hideyoshi late in the Sengoku period. Other notable examples include the supplanting of the Hosokawa clan by the Miyoshi, the Shiba clan by the Oda clan, and the Toki by the Saito. Well organized religious groups also gained political power at this time by uniting farmers in resistance and rebellion against the rule of the daimyo. The monks of the Buddhist True Pure Land sect formed numerous Ikkō-ikki, the most successful of which, in Kaga Province, remained independent for nearly 100 years.

Rise of Oda Nobunaga
During the last half of the 16th century, a number of different daimyo became strong enough either to manipulate the Muromachi bakufu to their own advantage or to overthrow it altogether. One attempt to overthrow the bakufu was made in 1560 by Imagawa Yoshimoto, whose march towards the capital came to an ignominious end at the hands of Oda Nobunaga in the Battle of Okehazama. In 1562, The Tokugawa clan who was adjacent to the east of Nobunaga's territory became independent of the Imagawa clan, and allied with Nobunaga. The eastern part of the territory of Nobunaga's was not invaded by this alliance. And, he moves the army to the west. In 1565, an alliance of the Matsunaga and Miyoshi clans attempted a coup by assassinating Ashikaga Yoshiteru, the 13th Ashikaga shogun. Internal squabbling, however, prevented them from acting swiftly to legitimatize their claim to power, and it was not until 1568 that they managed to install Yoshiteru's cousin, Ashikaga Yoshihide, as the next Shogun. Failure to enter Kyoto and gain recognition from the imperial court, however, had left the succession in doubt, and a group of bakufu retainers led by Hosokawa Fujitaka negotiated with Nobunaga to gain support for Yoshiteru's younger brother, Yoshiaki.

Nobunaga, who had prepared over a period of years for just such an opportunity by establishing an alliance with the Asai clan in northern Ōmi Province and then conquering the neighboring province of Mino Province, now marched toward Kyoto. After routing the Rokkaku clan in southern Omi, Nobunaga forced the Matsunaga to capitulate and the Miyoshi to withdraw to Settsu. He then entered the capital, where he successfully gained recognition from the emperor for Yoshiaki, who became the 15th Ashikaga shogun.

Nobunaga had no intention, however, of serving the Muromachi bakufu, and instead now turned his attention to tightening his grip on the Kansai region. Resistance in the form of rival daimyo, intransigent Buddhist monks, and hostile merchants was eliminated swiftly and mercilessly, and Nobunaga quickly gained a reputation as a ruthless, unrelenting adversary. In support of his political and military moves, he instituted economic reform, removing barriers to commerce by invalidating traditional monopolies held by shrines and guilds and promoting initiative by instituting free markets known as rakuichi-rakuza.

By 1573 he had destroyed the alliance of Asakura clan and Azai clans that threatened his northern flank, obliterated the militant Tendai Buddhists monastic center at Mount Hiei near Kyoto, and also had managed to avoid a potentially debilitating confrontation with Takeda Shingen, who had suddenly taken ill and died just as his army was on the verge of defeating the Tokugawa and invading Oda's domain on its way to Kyoto.

Even after Shingen's death, there remained several daimyo powerful enough to resist Nobunaga, but none were situated close enough to Kyoto to pose a threat politically, and it appeared that unification under the Oda banner was a matter of time.

Nobunaga's enemies were not only other Sengoku daimyō but also adherents of a Jōdo Shinshu sect of Buddhism who attended Ikkō-ikki. Their leader was Kennyo. He endured though Nobunaga kept attacking his fortress for ten years. Nobunaga expelled Kennyo in the eleventh year, but, by a riot caused by Kennyo, Nobunaga's territory took the big damage. This long war was called Ishiyama Hongan-ji War.

To suppress the Buddhism, Nobunaga supported Christianity. And, a lot of cultures were introduced to Japan by the missionary from Europe. Those things include new foods, new drawing methods, astronomy, geography, medical science, and new printing techniques.

Unification of Japan
After nearly a century and a half of political instability and warfare, Japan was on the verge of unification by Oda Nobunaga, who had emerged from obscurity in the province of Owari (present-day Aichi Prefecture) to dominate central Japan, when in 1582 Nobunaga himself fell victim to the treachery of one of his own generals, Akechi Mitsuhide. This in turn provided Toyotomi Hideyoshi, who had risen through the ranks from ashigaru (footsoldier) to become one of Nobunaga's most trusted generals, with the opportunity to establish himself as Nobunaga's successor. Hideyoshi eventually consolidated his control over the remaining daimyo and, although he was ineligible for the title of Seii Taishogun because of his common birth, ruled as Kampaku. He would later name his nephew, Toyotomi Hidetsugu, as Kampaku in 1592 following the death of Hideyoshi's half-brother, Toyotomi Hidenaga.

In the same year, Hideyoshi would launch his campaigns into Korea, now known as the Imjin War. The conflict would last from 1592 until 1598, with a brief truce in 1596. It would result in the Japanese failing to secure the peninsula.

At home, Hideyoshi and Hidetsugu's relationship had begun to deteriorate. Hidetsugu was accused of committing many murders that were deemed unjust. In 1595, he was accused of plotting a coup and later was ordered by Hideyoshi to commit seppuku on Mount Koya. Hidetsugu's family was later executed upon Hideyoshi's ordered, which was very controversial among daimyo. Hidetsugu and his family's deaths eventually led to the dissolution of the Toyotomi clan's authority post-Sekigahara.

When, in 1598, Hideyoshi died without leaving a capable successor, the country was once again thrust into political turmoil, and this time it was Tokugawa Ieyasu who took advantage of the opportunity.

Sekigahara, Creation of the Edo Shogunate, and Osaka
Before Hideyoshi's death, he assigned Tokugawa Ieyasu of the Kantō region, Ukita Hideie of Bizen and Mimasaka, Maeda Toshiie of Kaga and Etchū, Uesugi Kagekatsu of Yonezawa, Mōri Terumoto of Choshu, and Kobayakawa Takakage of Chikuzen to the Council of Five Elders. The council effectively ruled as regents to Hideyoshi's son and heir, Toyotomi Hideyori. However, following Hideyoshi's death in 1598, the council's relationship began to decline and by 1599, after the death of the "neutral" Maeda Toshiie, the conflicts had begun. Two factions then arose; the Bunchiha, which favored a civil service in Japan and the Bundanha, which favored a military government.

Ieyasu's influence was very large and was effectively a hegemony. He had organized many political marriages, securing alliances throughout Japan, including his son, Tadateru, to Date Masamune's daughter, Irohahime. This angered many council members, who believed that the marriages required approval from the council. The daimyō of Sawayama Castle, Ishida Mitsunari, then formed an alliance comprised of those opposed to the Tokugawa and were staunch Toyotomi chauvinists. Mitsunari eventually gained the support of Hideie, Kagekatsu, and Terumoto. Terumoto decided to stay within Osaka Castle, so field command was placed under Mitsunari. A factional dispute later arose between Ishida Mitsunari and several other generals under the Toyotomi banner, including Kato Kiyomasa of the Kumamoto domain. This allowed Tokugawa Ieyasu to persuade many daimyo to confront Mitsunari opposition to Ieyasu. In 1600, Uesugi Kagekatsu openly defied Tokugawa Ieyasu by building a castle in Aizu. Ieyasu had then demanded that Kagekatsu explained his actions, to which Kagekatsu refused. Kagekatsu had done this to distract Ieyasu to allow Mitsunari to enact his plan. However, Ieyasu had predicted this, and instead of personally leading a force against Kagekatsu, he had Mogami Yoshiaki and Date Masamune continue conflict against Kagekatsu in Tohoku.

Meanwhile, Ishida Mitsunari had finally launched his campaign. On 27 August, he began his siege of Fushimi Castle. He had hoped for a quick victory, but it turned into a ten day siege. The castle fell on 8 September and its defenders committed suicide. While Mitsunari achieved victory, he had lost the crucial time that was needed to secure an overall success in the campaign against Ieyasu. Mitsunari had hoped to use Gifu Castle as a point to delay the Tokugawa clan's advances. However, the castle fell to Ii Naomasa and Fukushima Masanori on 30 September. When realizing Tokugawa Ieyasu was marching towards Osaka Castle, Mitsunari revised his plans, and began to desire a direct confrontation at Sekigahara.

On 21 October, the battle of Sekigahara had begun. Ishida Mitsunari and his side comprised the Western Army, while Tokugawa Ieyasu and his side comprised the Eastern army. The battle had eventually stalemated, with both sides racking up casualties. Kobayakawa Hideaki, Toyotomi Hideyoshi's nephew, who had only accompanied Mitsunari with the intent of betrayal, finally defected to the Tokugawa clan's side. His force would begin to attack the positions of Otani Yoshitsugu, who'd eventually asked a retainer to behead him. After Hideaki's betrayal, the Western Army's front began to collapse. Meanwhile, Ii Naomasa was wounded in while chasing troops under the Shimazu clan. With no reinforcements incoming, the Western Army had been destroyed. However, Mitsunari was able to escape from the battlefield. He was later found and executed on 6 November.

In 1603, Emperor Go-Yozei bestowed the position of shogun to Tokugawa Ieyasu. This created the Tokugawa Shogunate, which is notable for its stability and peace. Ieyasu would later resign in 1605 in favor of his son, Tokugawa Hidetada. However, he still held control over the government.

However, Ieyasu still had one more major opponent, Toyotomi Hideyori. After tension between the two escalated in 1614, Ieyasu gathered a force of 160,000 and marched on Osaka Castle. This began the first phase of the siege of Osaka, the winter siege. Bombardment of the castle was heavy, but Osaka did not surrender. An uneasy treaty was then established between the two sides, but conflict began the next year once again. With the loss of the Battle of Tennoji, Osaka Castle on fire, and Sanada Yukimura's death, Hideyori and his mother committed seppuku as the castle burned around them. After their death's were announced, many other nobles committed suicide and the castle eventually surrendered, ending the Toyotomi clan and ending any major challenge to the Tokugawa's reign.

Tokugawa Ieyasu died on June 1, 1616 at the age of 73, becoming the last great unifier to die.

The Great Unifiers of Japan

 * Oda Nobunaga
 * Toyotomi Hideyoshi
 * Tokugawa Ieyasu

Other daimyo

 * Azai Nagamasa
 * Chōsokabe Motochika
 * Date Masamune
 * Hōjō Sōun
 * Ii Naotora
 * Imagawa Yoshimoto
 * Maeda Toshiie
 * Miyoshi Nagayoshi
 * Mōri Motonari
 * Ōtomo Sōrin
 * Saitō Dōsan
 * Sanada Masayuki
 * Shimazu Yoshihiro
 * Tachibana Muneshige
 * Tachibana Ginchiyo
 * Takeda Shingen
 * Uesugi Kenshin
 * Ukita Hideie

Other notable individuals

 * Akechi Mitsuhide
 * Fukushima Masanori
 * Fūma Kotarō
 * Hattori Hanzō
 * Honda Tadakatsu
 * Ii Naomasa
 * Ishida Mitsunari
 * Kato Kiyomasa
 * Maeda Keiji
 * Miyamoto Musashi
 * Mori Ranmaru
 * Naoe Kanetsugu
 * Oda Nobutada
 * Saika Magoichi
 * Sanada Yukimura
 * Sasaki Kojirō
 * Shibata Katsuie
 * Shima Sakon