Tojo, or outer-castle, system in Satsuma is unique in Japan under the Baku-Han Regime. The system was the basic unit in Satsuma's social structure. The system survived the enforcement of "Genna-no-ikkoku-ichijorei" (Order of Bakufu restricting the number of castles to one in each han). This paper is an attempt to give an account of the process of its establishment and consider the implications of the functions of such a system of social organization on Satsuma's internal and external policy.
Tojo-system was a social institution with decentralized military deployment. Under this system Shimazu, the feudal Lord of Satsuma, divided its territory into 113 districts. The administrative functions were performed by the distinctive samurai-group headed by jito. The office of jito was called "jito-kariya", and the zone of residence for the samurai group was named "funioto". The jito was entitled to serve as the commander who could mobilize the samurai group to form an army corp at an emergency. In Satsuma all the samurai, except for about 5, 000 Kagoshima jokashi (the castle town samurai), resided in fumoto living on farming. Those samurai were earlier called Tojo-shuju, or goshi later. The Tojo zones were not the same as those in the age of the Warring States. Most of them were settled in the early part of the Tokugawa Era under the new system that had replaced the older one.
The Tojo-system was constructed incrementally in the process of Shimazu's integration of three shu, or provinces: Satsuma, Osumi and Hyuga. There is some reasonable ground for identifying the year of the establishment of this system as around the fifth year of Keicho (1600).
The Shimazu family founded its dictatorship in 1600 after the long battles that ravaged the area since 1526 when Takahisa succeeded the dynasty. The Shimazu successively conquered the antagonistic local clans in the domain, with the final battle ending in the defeat of Ijuin Kogan (Shonai-no-ran, 1599-1600).
Around the mid-1590s Toyotomi Hideyoshi, the Grand Warrior Lord of the nation, ordered a land survey (1594-1595), which benefited the Shimazu as they conducted-a large-scale replacement of the leading vassals to achieve their hegemony.
As a step toward integration the Shimazu started to build new Tojo as well as to re-arrange the existing ones throughout the territories. Because of their strategic importance the Tojo at the border, such as Izumi on the gateway to Higo, Okuchi to Kuma, and Takaoka and Shibushi to Hyuga, commanded Shimazu's most serious attention. Shimazu placed his most trusted and influential samurai heads to those places where they promoted drastic social reforms and set up a strict control system for the trans-border traffic.