Buke (Samurai Families) (武家)
The word "buke" refers to the collection of various powers which support the authority of a bakufu (Japanese feudal government headed by a shogun), and this word sometimes also refers to a Shogun family or general samurai.
In the society of the nobility of the middle Heian period, the trend of the "succession of family business" rapidly became popular, and only specific families began to occupy certain government official posts or occupations. On the other hand, lower-ranked nobles whose function was to be skilled in the military arts had also developed their own family characteristics specialized in the military arts, and such families were called "tsuwamono no ie" (literally, "soldier family"). Subsequently, some of such families began to play a key role as the military elite at the dawn of samurai. It is said that people began to use the terms 'buke,' 'buyu no ie' (a house of heroes), and 'bumon' (a samurai clan) in order to refer to those lineages or families. These terms also implied lineages who served the Imperial Family (or an emperor) with their military power and bravery. After the Kamakura bakufu was established in the eastern part of Japan, the term "buke" came to mean the bakufu and Kamakura-dono (the lord of Kamakura).
This reflected the fact that the bakufu and Kamakura-dono (MINAMOTO no Yoritomo) promised to serve the Imperial Court with their military power and the Imperial Court officially approved the military-police authority of the bakufu and Kamakura-dono in return. Once people became accustomed to referring to the Kamakura bakufu as buke, another new word 'kuge,' which was a general term representing civil officials at the Imperial Court, appeared. The use of these two terms was based on the comparison of their services to the Imperial Family, namely "kuge" in charge of general government affairs and "buke" in charge of military affairs. In the beginning of the Kamakura period, the Imperial Court had called the bakufu buke or Kanto (derived from the "Kanto region"), but once the bakufu installed Rokuhara Tandai (an administrative and judicial agency in Rokuhara, Kyoto) in order to monitor the Imperial Court after the Jokyu War, the term "buke" came to indicate Rokuhara Tandai only, while the bakufu was simply called Kanto.
Among ordinary people, however, the term "buke" came to be commonly used to address the bakufu, their various agencies, and their authority. Furthermore, the term also came to encompass gokenin (immediate vassals of the shogun in the Kamakura and Muromachi periods) who were regarded as the rank and file of the bakufu that enforced the influence of the bakufu. In the Muromachi period, the term "buke" indicated the Muromachi bakufu and the Shogun family, while in the Edo period, the term came to cover not only the bakufu and the Shogun family but also various daimyo (Japanese feudal lords) and high-ranked samurai.
It is believed that people except for samurai, namely peasants and townsmen, referred to all samurai as buke. During the Edo period, Imperial posts assigned to buke such as daimyo were regarded as ingai-kan (supernumerary positions), and these positions had nothing to do with traditional posts given to kuge even if they had the same post names; additionally, samurai at these positions were excluded from the prescribed number of personnel of such traditional posts. Therefore, such "Imperial posts" were rather very nominal ones used for the purpose of ranking.
It is thought that such posts were often used without approval of the Imperial Court.
(For more details, please refer to Buke-Kani (Official Court Titles for Samurai.)
A post which could be allotted to a certain buke was strictly specified according to the rank of that daimyo. This ranking system was used by the Edo bakufu to maintain its bakuhan taisei (feudal system characteristic of the shogunate).