Oban (the great guards) (大番)
Oban (the great guards) was one of the organizations of the Edo bakufu (Japanese feudal government headed by a shogun). It was the troop which was formed by organizing hatamoto (direct retainers of the Edo bakufu) as a standing force.
Oban as a standing force was the oldest force among the similar organization called gobangata (the collective name of five military organizations in the Edo period: kosho-gumi [the page corps], shoinban [the castle guards], shinban [the new guards], oban [the great guards], and kojunin [the escort guards]). Oban was organized in 1586, the year following the Kazumasa ISHIKAWA's escape, when Ieyasu TOKUGAWA changed his military system to the system used in the army of Takeda. Six people including Nobumasa NAITO were installed as the first oban-gashira (the captains of the great guards). In 1592, with the reconstruction of Edo Castle, the six residences were moved from the previous places and situated in the east side of Edo Castle.
(In Chiyoda-ku, the six districts, from Ichiban-cho to Rokuban-cho [from the first district to the sixth district], whose names are related to the six residential sites, still remain.)
Before the Edo period began, the Matsudaira clan and the relatives of Ieyasu were often hired as the captain of oban. At the time, oban had a role as the bodyguard which was later succeeded by ryoban.
At first, oban consisted of six units. Following the enhancement of oban and the improvement of the bakufu system, oban consisted of twelve units, serving as Honmaru-roju-shihai. When Tadahide TOKUGAWA was installed as Shogun, Shoinban and Koshogumi (originally it was called Hanabatake-ban [literally, "Guards at the Flower Garden" because there was a flower garden in front of Kuroshoin-saikonoma, the first place where Koshogumi guarded]) were newly created. The role as a guardian was taken over by shoinban and koshogumi and oban gradually became a military force under the direct control of the Edo bakufu. Since Oban was not the guardians of a shogun, an ogosho (a retired shogun), and a seishi (the heir), oban was not placed to Nishinomaru (the western enceinte).
One oban unit consisted of one ban-gashira (the captain), four kumi-gashira (the leaders), fifty banshi (the guards), ten yoriki (the constables), and twenty doshin (the policemen). Bangashira held a fief of 5,000 koku and was given the shiko-seki (a waiting place, arranged in descending order of rank, to have an audience with shogun). Often a daimyo was installed as a ban-gashira (especially, such tendency was often seen during the early years of the Edo bakufu). Kumigashira, with a fief of 300 koku and a salary of 100 sacks of rice, was given the tsutsujinoma-seki (a waiting place, arranged in descending order of rank, to have an audience with a shogun). The hatamoto with a fief of about 200 koku was installed as banshi, although the installation to banshi was decided by the amount of his fief (the shortfall was not covered by the ashidakasei [a wage system that guaranteed standardized compensation by the Tokugawa bakufu officials]). The total military forces calculated by the number of banshi who joined the military service which was decided on the basis of the yakudaka (the amount of the person's fief) were over four hundreds. The number was equal to the total military forces of the daimyo with about a fief of 20,000 koku.
(According to "Iwabuchiyawa" [Night Stories of Iwabuchi], the number was equal to the total military forces of the daimyo with a fief of 50,000 koku.)
In wartime, as the vanguard of a hatamoto troop, oban with various ashigaru-gumi (the teams of the lowest-rank samurai) served as cavalry for defense against an attack by the enemy. In peacetime, oban guarded Edo Castle town and other important places. The important places where oban guarded were Nijo Castle and Osaka Castle. Two pairs of oban were assigned to each castle as the guard, working in alternate one-year shifts. In the early Edo period, in addition to Nijo Castle and Osaka Castle, oban guarded Fushimi Castle and Sunpu Castle; however, the guard of Fushimi Castle and Sunpu Castle were abolished because Fushimi Castle was razed and the guard of Sunpu Castle was taken over by shoinban.
Although oban was the oldest military organization, the social standing was lower than koshogumi and shoinban which were called "ryoban." Due to this fact, the banshi had limited career ladder opportunities. In Satsuma Domain, until the social ranks were organized, the samurai whose family ranks were later divided into okoshogumi and shinban (new guards) were called oban.