Sengoku period

During this period, although the Emperor of Japan was officially the ruler of the state and every lord swore loyalty to him, he was largely a marginalized, ceremonial, and religious figure who delegated power to the shōgun, a noble who was roughly equivalent to a military dictator.

From 1346 to 1358, during the Nanboku-cho period, the Ashikaga shogunate gradually expanded the authority of the shugo, the local military and police officials established by the Kamakura shogunate, giving the shugo jurisdiction over land disputes between gokenin and allowing the shugo to receive half of all taxes from the areas they controlled. The Shugo shared their newfound wealth with the local samurai, creating a hierarchical relationship between the shugo and the samurai, and the first early daimyo, called shugo daimyo, appeared.

In 1428, Ashikaga Yoshimochi, the fourth Ashikaga shogun, was ill and the question of his succession arose. Ashikaga Yoshikazu, the 5th Ashikaga shogun, died of illness at the age of 19, so the 6th Ashikaga shogun was chosen from among Yoshimochi's four brothers, and to ensure fairness, a lottery was held. The sixth Ashikaga shogun was Ashikaga Yoshinori. He was not educated to be shogun, and his temperamental and despotic behaviour caused resentment. Akamatsu Mitsusuke assassinated him during the Kakitsu Rebellion. This led to instability in the Ashikaga shogunate system. The shogunate gradually lost influence and control over the daimyo.

The beginning of the Sengoku Period is considered to be the Kyōtoku incident, Ōnin War, or Meiō incident.

The Kyōtoku Incident was a major war in the Kanto region that lasted from 1454 to 1482. The war began when Ashikaga Shigeuji of Kantō kubō, the office of the Ashikaga shogunate in charge of the Kanto region, killed Uesugi Noritada of Kantō Kanrei, Kantō kubō's assistant. The various forces in the Kanto region divided and fought between the Kubō and Kanrei sides, with the Ashikaga shogunate supporting the Kanrei side.

Ashikaga Yoshimasa, the 8th Ashikaga shogun, tried to strengthen the power of the shogun, but his close associates did not follow his instructions, leading to political chaos and increasing social unrest. Since he had no sons, he tried to install his younger brother Ashikaga Yoshimi as the ninth shogun, but when his wife Hino Tomiko gave birth to Ashikaga Yoshihisa, a conflict arose among the shugo daimyo as to whether Yoshimi or Yoshihisa would be the next shogun. The Hatakeyama and Shiba clans were also divided into two opposing factions over succession within their own clans, and Hosokawa Katsumoto and Yamana Sōzen, who were father-in-law and son-in-law, were politically at odds with each other.

In 1467, these conflicts finally led to the Ōnin War (1467–1477) between the Eastern Army, led by Hosokawa Katsumoto and including Hatakeyama Masanaga, Shiba Yoshitoshi, and Ashikaga Yoshimi, and the Western Army, led by Yamana Sōzen and including Hatakeyama Yoshinari, Shiba Yoshikado, and Ashikaga Yoshihisa. In 1469, the war spread to the provinces, but in 1473, Hosokawa Katsumoto and Yamana Sōzen, the leaders of both armies, died. In 1477, the war ended when the western lords, including Hatakeyama Yoshinari and Ōuchi Masahiro, withdrew their armies from Kyoto.

The war devastated two-thirds of Kyoto, destroying many aristocratic and samurai residences, Shinto shrines, and Buddhist temples, and undermining the authority of the Ashikaga shoguns, greatly reducing their control over the various regions. The war caused disarray which rippled across Japan. In addition to the military confrontations between separate states, there was also domestic fallout. In contempt of the shogunate, the daimyo who were subjected to remain in Kyoto instead returned to their provinces. Consequentially, some of these daimyo found that their designated retainers or shugodai, representatives of their states appointed in a daimyo's absence, rose in power either to seize control of the domain or proclaim independence as a separate domain.

Thus began the Sengoku period, a period of civil war in which the daimyo of various regions fought to expand their own power. Daimyo who became more powerful as the shogunate's control weakened were called sengoku daimyo, and they often came from shugo daimyo, shugodai, and kokujin or kunibito (国人, local masters). In other words, sengoku daimyo differed from shugo daimyo in that a sengoku daimyo was able to rule the region on his own, without being appointed by the shogun.

Historians often consider the Ōnin War, a ten-year conflict wrought by political turmoil, to be the trigger for what would come to be known as the Sengoku period. This civil war would clearly reveal the Ashikaga shogunate's reduced authority over its shogunal administration, the provincial daimyo and Japan as a whole; thereby a wave of unbridled conflict would spread across Japan and consume the states in an age of war. Furthermore, weariness of war, socioeconomic unrest and poor treatment by aristocrats provoked the wrath of the peasant class. Farmers, craftsmen, merchants and even villages would organize uprisings (known as "ikki") against the ruling class. An extraordinary example is the Kaga Rebellion, in which the local ikki had staged a large-scale revolt with the support of the True Pure Land sect (thereby establishing the term ikkō ikki) and assumed control of the entire province of Kaga. It is suggested by both scholars and authors that "these succession disputes still might not have led to war were it not for the shōgun's lack of leadership."

The Kyōtoku incident in 1454, Ōnin War in 1467, or Meiō incident in 1493 is usually considered the starting point of the Sengoku period. There are several events which could be considered the end of it: Nobunaga's entry to Kyoto (1568) or abolition of the Muromachi shogunate (1573) or entry into Azuchi Castle (1576), Hideyoshi's promulgation of the Sōbujirei law prohibiting war (1587), the siege of Odawara (1590), the Battle of Sekigahara (1600), the establishment of the Tokugawa shogunate (1603), the siege of Osaka (1615), or the suppression of the Shimabara Rebellion (1638). The old, well-known definition is that the Onin War initiated the Sengoku period in 1467; and that it ended in 1568, when Oda Nobunaga entered Kyoto in support of Ashikaga Yoshiaki.

However, even if 1568 is the end date of the Sengoku period, there are also various theories about the beginning and end dates of the following Azuchi-Momoyama period. The Azuchi-Momoyama period refers to the period when Oda Nobunaga and Toyotomi Hideyoshi were in power. They and Tokugawa Ieyasu are the three unifiers of Japan. The name "Azuchi-Momoyama" comes from the fact that Nobunaga's castle, Azuchi Castle, was located in Azuchi, Shiga, and Fushimi Castle, where Hideyoshi lived after his retirement, was located in Momoyama. The beginning date could be either when Oda Nobunaga entered Kyoto in 1568 to support Ashikaga Yoshiaki, or when Nobunaga expelled Ashikaga Yoshiaki from Kyoto in 1573 and destroyed the Muromachi Shogunate, or when Nobunaga moved to Azuchi Castle in 1576. It ended either when Toyotomi Hideyoshi died in 1598, or at the Battle of Sekigahara in 1600, or with the opening of the Tokugawa shogunate in 1603.

Kaga ikki occurred in 1488, Hōjō Sōun conquered Izu province in 1491, and in 1492 Hosokawa Masamoto banished the 10th shogun Ashikaga Yoshitane from Kyoto and installed Ashikaga Yoshizumi as the 11th shogun. Around this time, civil wars began to occur frequently throughout the country, and Buddhist temples in various regions grew as armed forces.

Ashikaga Yoshihisa, who had become the ninth shogun during the Onin War, died at the age of 25, and Ashikaga Yoshitane became the 10th shogun. However, in 1493, Hosokawa Masamoto raised an army while shogun Yoshitane was away in Kyoto and installed the 11th shogun, Ashikaga Yoshizumi, in a de facto coup known as the Meiō incident (明応の政変). Masamoto held the position of Kanrei, second only to the shogun in the Ashikaga shogunate, and the equivalent of Shikken in the Kamakura shogunate. This made the shogun a puppet of the Hosokawa clan, which served as the Kanrei. In recent years, it has been theorized that this incident marked the beginning of the Sengoku period.

Hosokawa Masamoto remained a bachelor for the rest of his life and adopted three people as his heirs. Following the advice of his vassals, Masamoto named Hosokawa Sumimoto as his successor instead of Hosokawa Sumiyuki, who had been adopted first. As a result, Masamoto was killed by Sumiyuki in 1507. This incident is called Eishō no sakuran (永正の錯乱, Eishō delirium). This triggered a struggle for the succession of the Hosokawa clan, which was divided into the Hosokawa Sumimoto faction and the Hosokawa Takakuni faction, and started a war called Ryō Hosokawa War (両細川の乱), which was won by Hosokawa Takakuni.

Hosokawa Takakuni installed Ashikaga Yoshiharu as the 12th shogun. Meanwhile, Hosokawa Harumoto, son of Hosokawa Sumimoto, who had lost the war, collaborated with Miyoshi Motonaga to defeat Takakuni at the Battle of Katsuragawa (桂川の戦い) in 1527 and expel him from Kyoto. The authority of the Kanrei was thus destroyed, and with almost no support for Hosokawa Takakuni, he was forced to move from place to place. He gained the sengoku daimyo Uragami Muramune as an ally and fought Hosokawa Harumoto in a war called Daimotsu kuzure (大物崩れ) in 1531, but was defeated.

Hosokawa Harumoto seized power, but he alienated Miyoshi Motonaga, who was his retainer but still held a strong position of power. Harumoto seduced the Ikkō-shū into a Ikkō-ikki against Motonaga, which resulted in Motonaga's death in 1532.

Miyoshi Motonaga's son, Miyoshi Nagayoshi, fought against Hosokawa Harumoto, but chose to subordinate himself to Harumoto. As a follower of Harumoto, Miyoshi Nagayoshi defeated Kizawa Nagamasa, the most powerful member of the Hatakeyama clan who served as Kanrei, and in 1547 defeated the 12th shogun, Ashikaga Yoshiharu and Hosokawa Ujitsuna, son of Hosokawa Takakuni, in the Battle of Shari-ji (舎利寺の戦い). This further reduced the power of the Ashikaga Shogunate. Miyoshi Nagayoshi was told by a retainer of the Hosokawa family that Miyoshi Masanaga had played a dark role in his father's death, and he petitioned his lord Hosokawa Harumoto to overthrow Masanaga, but this petition was not accepted, and, in turn, Nagayoshi was almost eliminated by Harumoto. In response, Miyoshi Nagayoshi attacked and defeated Miyoshi Masanaga, expelled Hosokawa Harumoto, Ashikaga Yoshiharu, the 12th shogun, and his son Ashikaga Yoshiteru from Kyoto, and established control over the Kyoto area in 1549. After that, he fought several times against Ashikaga Yoshiteru, who became the 13th shogun, for control of the Kyoto area. However, one by one, his sons died in war or from disease, and the Miyoshi clan began to decline rapidly.

By the time of the 13th shogun, Ashikaga Yoshiteru, the shogun already had few direct fiefs and direct military forces, and his sphere of influence was limited to a few lands around Kyoto, losing both economic and military power. As a result, Ashikaga Yoshiteru was often chased out of Kyoto by the sengoku daimyo Miyoshi Nagayoshi and his forces, and was finally killed in an attack by the forces of Miyoshi Yoshitsugu and Matsunaga Hisahide. Ashikaga Yoshiteru was known as a great swordsman and was a student of Tsukahara Bokuden, who was known as one of the strongest swordsmen. According to Yagyū Munenori, a swordsmanship instructor in the Tokugawa Shogunate, Ashikaga Yoshiteru was one of the five best swordsmen of his time. According to several historical books, including Luís Fróis' Historia de Japam, he fought hard with naginata and tachi during a raid, defeating many of his enemies, but eventually ran out of strength and was killed.

The trio (三好三人衆) of Miyoshi Nagayasu, Miyoshi Soui, and Iwanari Tomomichi supported the young head of the clan, Miyoshi Yoshitsugu, in leading the Miyoshi clan. However, after the assassination of the 13th Shogun, the trio fell out with another Miyoshi follower, Matsunaga Hisashige, over the 14th Shogun, Ashikaga Yoshihide, and war broke out. The latter three also came into conflict with Yoshitsugu. The Miyoshi regime virtually collapsed when Oda Nobunaga entered Kyoto in 1568. Miyoshi Yoshitugu and Matsunaga Hisahide submitted to Nobunaga, but were later killed by Nobunaga's forces. The trio was weakened and the Miyoshi clan declined.

Mōri Motonari was a sengoku daimyo who pacified the Chūgoku region and is famous for his parable of the "Three Arrows", which explains the importance of clan unity. In his first battle, the Battle of Arita-Nakaide in 1517, he defeated the overwhelming majority of the Aki-Takeda clan with a small force, which later became known as the "Battle of Okehazama in the West" as a battle in which a small force defeated a large army. Motonari became head of the Mōri clan in 1523 at the age of 27. The Amago and Ōuchi clans were sharing power in the Chūgoku region at the time, and he switched the Mōri clan's allegiance from the Amago to the Ōuchi clan in 1525. Motonari destroyed the Takahashi clan by 1535 and ruled Aki Province, Iwami Province, and Bingo Province, and destroyed the Aki-Takeda clan at the siege of Yoshida-Kōriyama Castle in 1541. Motonaga adopted his sons into the Kikkawa clan and Kobayakawa clans to expand the power of the Mōri clan, and the three clans cooperated with each other. In 1554, Motonaga became independent of the Ōuchi clan, and after inciting the Ōuchi clan to internal divisions through political maneuvering, he defeated Sue Harukata, who had been in control of the Ōuchi clan, at the Battle of Itsukushima in 1555, and defeated Ōuchi Yoshinaga in 1557, destroying the Ōuchi clan and pacifying Nagato and Suou provinces.

Motonari destroyed the Amago clan at the siege of Gassantoda Castle in 1567, and then pacified Izumo, Oki, and Hōki Provinces, thus pacifying the Chūgoku region, and later extended his power to parts of Shikoku. He died in 1571 at the age of 75.

In 1546, Hōjō Ujiyasu defeated Uesugi Tomosada at the siege of Kawagoe Castle, and the Later Hōjō clan established its power in the Kantō region.

Uesugi Kenshin (Nagao Kagetora) was a sengoku daimyo based in Echigo Province who fought various sengoku daimyo and increased his power through aggressive invasions. After unifying Echigo in 1551, he invaded the Kantō region several times from 1552 to 1569 and fought against Hōjō Ujiyasu. He also invaded the territory of Takeda Shingen, who ruled Kai and Shinano Provinces from 1553 to 1573, and fought in the Battle of Kawanakajima five times between 1553 and 1564. In 1559, Kenshin had an audience with Emperor Ōgimachi and the 13th Shogun, Ashikaga Yoshiteru. When Imagawa Yoshimoto was killed by Oda Nobunaga's forces at the Battle of Okehazama in 1560, the Alliance Kai-Sagami-Suruga formed in 1554 between Takeda Shingen in Kai, Hojo Ujiyasu in Sagami, and Imagawa Yoshimoto in Suruga was broken. Kenshin used this as an opportunity to seize Hojo Ujiyasu's territories one by one, and cornered the Later Hōjō clan at the siege of Odawara in 1561, but was unable to defeat them. On his return from the siege of Odawara, he performed a ceremony at the Tsurugaoka Hachimangū and assumed the position of kantō kanrei. Kenshin made peace with Hōjō Ujiyasu, who ceded part of his territory to him in 1569, and made Takeda Shingen a common enemy of Kenshin and Ujiyasu, but Shingen died of illness in 1573. After Takeda Shingen's death, he fell out with Oda Nobunaga and destroyed the Noto Hatakeyama clan, which was close to Nobunaga, at the siege of Nanao in 1577, pacifying Noto Province. He then defeated Oda Nobunaga's forces at the Battle of Tedorigawa. However, he died of a cerebral hemorrhage in 1578 at the young age of 49.

When the Portuguese brought the matchlock gun to Japan in 1543, it was mass-produced in Japan, and a gun called the tanegashima began to be used in wars. With the introduction of guns, a standing army of ashigaru (foot soldier) became essential to victory in war, making it impossible for small local lords to remain independent, and lands were consolidated under sengoku daimyo with vast territories, and battles between sengoku daimyo became more intense.

During this period, the organized use of large numbers of tanegashima (guns) was essential to winning the war. In order for the daimyo to win the war, they had to secure a large number of gunsmiths and arms dealers, import large quantities of lead, the raw material for bullets, and nitre, the raw material for gunpowder, conduct routine marksmanship training, and secure large quantities of materials for building war positions. It was Oda Nobunaga who did this most successfully. He built Azuchi Castle at a strategic distribution point, brought several gunsmithing centers under his control, and established friendly relations with the Portuguese and merchants in Sakai, which had become an international port. He examined the rice yields of the lands under his control and did not allow his retainers to take private ownership of the lands, leaving the management of the lands to his retainers. This made it possible to efficiently change territories according to the performance of the vassals, thus eliminating land disputes. In addition, he made it possible to form a standing army by assigning military service to each region according to rice production.

The upheaval resulted in the further weakening of central authority, and throughout Japan, regional lords, called daimyōs, 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 emancipated aristocracy, became known as gekokujō, which means "low conquers high".

One of the earliest instances of this 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 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 Toki by the Saitō, and the Shiba clan by the Oda clan, which was in turn replaced by its underling, Toyotomi Hideyoshi, a son of a peasant with no family name.

Well-organized religious groups also gained political power at this time by uniting farmers in resistance and rebellion against the rule of the daimyōs. 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.