Sengoku Jidai

During this period, although the Emperor of Japan was officially the ruler of his nation 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 general. In the years preceding this era, the shogunate gradually lost influence and control over the daimyōs (local lords). Many of these lords began to fight uncontrollably with each other for control over land and influence over the shogunate.

After the Ōnin War, the Ashikaga bakufu completely fell apart; for all practical purposes, the Hosokawa family was in charge and the Ashikaga shōguns became their puppets. The Hosokawa family controlled the shogunate until 1558 when they were betrayed by a vassal family, the Miyoshi. The powerful Ōuchi were also destroyed by a vassal, Mōri Motonari, in 1551. Kyoto was devastated by the war, not really recovering until the mid-16th century.

The Kaga Rebellion or Chōkyō Uprising was a large-scale revolt in Kaga Province (present-day southern Ishikawa Prefecture), Japan, in late 1487 through 1488. Togashi Masachika, who ruled Kaga Province as shugo, had been restored to power in 1473 with aid from the Asakura clan as well as the Ikkō-ikki, a loose collection of lesser nobility, monks, and farmers. By 1474, however, the Ikkō-ikki grew discontent with Masachika, and launched some initial revolts, which were easily quelled. In 1487, when Masachika left on a military campaign, between 100,000 and 200,000 Ikkō-ikki revolted. Masachika returned with his army, but the Ikkō-ikki, backed by several disaffected vassal families, overwhelmed his army and surrounded him in his palace, where he committed seppuku. The former vassals of Masachika granted the position of shugo to Masachika's uncle Yasutaka, but over the next several decades, the Ikkō-ikki increased their political hold on the province, which they would effectively control for almost a century.

During the 15th century in Japan, peasant revolts, known as ikki, became much more commonplace. During the turmoil of the Ōnin War (1467–1477) and subsequent years, these rebellions increased in both frequency and success. Many of these rebels became known as Ikkō-ikki, a collection of peasant farmers, Buddhist monks, Shinto priests, and jizamurai (lesser nobles) who all espoused belief in the Jōdo Shinshū sect of Buddhism. Rennyo, the Hongan-ji abbot who led the Jōdo Shinshū movement, attracted a large following in Kaga and Echizen Province, but distanced himself from the political goals of the ikki, advocating violence only for self-defense or defense of one's religion.During the mid-15th century, a civil war broke out among the Togashi clan over the position of shugo.

This was part of a failed attempt by the Uesugi clan to regain Kawagoe Castle from the Later Hōjō clan. This Hōjō victory marked the decisive turning point in the struggle for the Kanto region. The Hōjō tactics which said to be "the one of the most notable examples of night fighting in samurai history". This defeat for the Uesugi would lead to the near-extinction of the family, and with Tomosada's death, the Ōgigayatsu branch came to an end.

In this battle, the heavily outnumbered Oda clan troops commandeered by Oda Nobunaga defeated Imagawa Yoshimoto and established himself as one of the front-running warlords in the Sengoku period. The Battle of Okehazama is regarded as one of the most significant turning points in Japanese history. The Imagawa clan was greatly weakened and would soon be destroyed by its neighbors. Oda Nobunaga gained greatly in prestige, and many samurai and minor warlords (including Imagawa's former retainer, Matsudaira Motoyasu, the future Tokugawa Ieyasu) pledged fealty.

Toyotomi Hideyoshi defeats the Hōjō clan, unifying Japan under his rule. The third siege of Odawara was the primary action in Toyotomi Hideyoshi's campaign to eliminate the Hōjō clan as a threat to his power. Tokugawa Ieyasu, one of Hideyoshi's top generals, was given the Hōjō lands. Though Hideyoshi could not have guessed it at the time, this would turn out to be a great stepping-stone towards Tokugawa's attempts at conquest and the office of Shōgun.

The invasions were launched by Toyotomi Hideyoshi with the intent of conquering the Korean Peninsula and China, which were respectively ruled by the Joseon and Ming dynasties. Japan quickly succeeded in occupying large portions of the Korean Peninsula, but the contribution of reinforcements by the Ming, as well as the disruption of Japanese supply fleets along the western and southern coasts by the Joseon navy, forced a withdrawal of Japanese forces from Pyongyang and the northern provinces to the south in Busan and nearby regions. Afterwards, with righteous armies (Joseon civilian militias) launching guerrilla warfare against the Japanese and supply difficulties hampering both sides, neither were able to mount a successful offensive or gain any additional territory, resulting in a military stalemate. The first phase of the invasion lasted from 1592 until 1596, and was followed by ultimately unsuccessful peace negotiations between Japan and the Ming between 1596 and 1597.

Hideyoshi sent approximately 200 ships with an estimated 141,100 men under the overall command of Kobayakawa Hideaki. Japan's second force arrived unopposed on the southern coast of Gyeongsang Province in 1596. However, the Japanese found that the Korean army was both better equipped and better prepared to deal with an invasion than several years prior.

The period culminated with a series of three warlords – Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu – who gradually unified Japan. After Tokugawa Ieyasu's final victory at the siege of Osaka in 1615, Japan settled down into over 200 years of peace under the Tokugawa shogunate.