Gekokujo ("the low overturning the high," a term used to describe retainers overthrowing their lords) describes situations in Japanese history that occur when a person of lower rank overthrows a superior either politically or militarily, and then supplants the superior's position in society.
As a term, gekokujo was in use from the Kamakura period through to the period of the Northern and Southern Courts (Japan); examples of gekokujo include the scoundrels that started to appear near the end of the Kamakura period who fought against the authorities in order to protect their own vested interests, as well as the anti-authoritarian social movement known as "basara" ("vajra" in Sanskrit) that occurred during the Nanbokucho period. Basara activities were banned in the Kenmu Code, which was the fundamental code of laws for the shogunate established by Takauji ASHIKAGA in 1336.
The term also appeared in the phrase "Those who establish themselves by gekokujo (overthrowing their lords)" in the book "Scrawlings from the Nijo gawara," coming to be used as a symbol of the social tendencies of the Sengoku Period (Period of Warring States) in Japan. When we look back on historic situations where a lower-ranked group usurped the authority of their superiors, as when the aristocracy was overthrown by the samurai class, the Shogun by the Kanrei (shogunal deputy), and the Protectors (essentially provincial governors) by their deputy Protectors, we label it "gekokujo," but for people in fact in the Sengoku Period, such situations were more or less par for the course. Furthermore, cases where members of a given family usurped the position of head of the family and made themselves daimyo (territorial lords) are too numerous to count; examples include Tadayoshi SHIMAZU, Harumasa NANBU, and Yoshitaka SATOMI.
One point of view holds that the custom of shukun oshikome (shutting away/neutralizing one's lord) often seen among the warrior society in the Kamakura period is another type of gekokujo. In the samurai society of the medieval period, the existence and position of a lord was not necessarily guaranteed or absolute to his retainers; instead, lords and their group of retainers had a shared fate, and their relationship was one of mutual cooperation. As a result, those lords who ignored the desires and ideas of their retainers were often driven from power and replaced by someone else via a meeting of the retainers, and occasionally a powerful retainer would install himself as the new lord with the support of the group of retainers. This sort of tendency is a striking feature of the Muromachi period; Shogun Yoshinori ASHIKAGA being assassinated by the Akamatsu clan (in the Kakitsu Revolt), Shogun Yoshiki ASHIKAGA being driven from power by Masamoto HOSOKAWA and replaced (in the Meio Coup), and Shogun Yoshiteru ASHIKAGA's assassination by Hisahide MATSUNAGA can all be understood as examples of shukun oshikome (shutting away/ neutralizing their lords) against the Shogunal family. In addition to these examples, there were frequently cases, such as the Protector family of Kawachi Province and the Hosokawa clan, who held the position of Kanrei, where deputy Protectors (shugo) drove their lords from power and replaced them; other cases of shukun oshikome include when Harukata SUE engineered the banishment and annihilation of Yoshitaka OUCHI, and when Shingen TAKEDA brought about the exile of his own father, Nobutora TAKEDA.
In this way, the mainstream view on the central principle underlying the unstable political situation during the Sengoku Period gradually shifted from thinking it was gekokujo to people simply taking power for themselves via shukun oshikome. The control that the daimyo in the Sengoku Period extended over their territories was definitely not autocratic; instead, it was premised on the approval and inclinations of their group of retainers. When looked at from this viewpoint, it is possible to see the system by which daimyo in the Sengoku Period ruled their domains as having come into existence via cooperation and solidarity between the daimyo and their groups of retainers. The lords who ignored--or worse yet, despised--the will and inclination of their group of retainers were likely to experience the misery of being deposed and replaced, and judged a fitting target for gekokujo by society. Yet, starting from the establishment of Hideyoshi TOYOTOMI's government, situations of shukun oshikome calmed down, and were not seen inside the Tokugawa family itself (which held the shogunate), but shukun oshikome remained comparatively frequent among the various daimyo.
A list of famous examples of gekokujo
In 1441, the sixth Ashikaga Shogun, Yoshinori, was assassinated by Mitsusuke AKAMATSU and his son during the Kakitsu Rebellion.
In 1493, the tenth Ashikaga Shogun, Yoshitane, was deposed by Masamoto HOSOKAWA and allies and replaced by the eleventh Ashikaga Shogun, Yoshizumi, while Masamoto himself assumed de facto leadership of the shogunate.
In 1551, Dosan SAITO drove his lord the Protector Yorinari TOKI into exile and he himself became lord of Mino Province.
In 1582, there was an Incident at Honnoji temple. During the incident, Nobunaga ODA was the victim of an insurrection by his vassal Mitsuhide Akechi.
So, in 1582, the vassals of the Oda family gathered at Kiyosu castle in Owari Province (modern-day Aichi Pref.), and began their meeting (the Kiyosu meeting) to determine the rightful successor to the slain Nobunaga ODA. Hideyoshi TOYOTOMI, who had the greatest record of achievements after hunting down and killing Mitsuhide AKECHI--the ringleader of the Incident at Honnoji temple--nominated Hidenobu ODA, the grandson of Nobunaga, as a puppet ruler (Hidenobu was only two at the time), thereby usurping the lion's share of successional power for himself.