The term Kashindan refers to the group of vassals serving samurai families, such as the family of the Seii Taishogun (literally, a general who subsides barbarians) or a daimyo (Japanese territorial lord).
The relationship between master and vassal until the medieval period
Until the medieval period, samurai within a master and vassal relationship who were subordinate to a Bumon no toryo (leader of samurai families) were called Kenin. Most Kenin during the Heian period were descendants of a Gunji (local magistrate) or Dogo (local powerful clan) and were engaged in the administration of the Kokufu (provincial government office) as local officials. Meanwhile, they evaded heavy taxes imposed by the Kokufu and prevented intervention by the Imperial Court by donating shoen (manor) to Ingu oshinke (a general term for Imperial families and nobilities) and influential temples and shrines. At the same time, they rendered homage and service to a Bumon no toryo, who held great provincial power due to their noble bloodline and close relationship with the Imperial Court and powerful nobilities; they did so in return for honryo-ando (acknowledgement of inherited territories) so that they could get out of trouble under the protection of the Bumon no toryo in the event of military attack. In other words, many local samurai managed to secure independence, survival and opportunities to expand their territory by establishing multiple relationships with powerful and influential individuals who shared mutual interests. As the relationship between master and vassal among samurai was highly dependent on interests, at times vassals would abandon a Bumon no toryo, if and when they came under an unfavorable situation due to a war and changed loyalty to the opponent. As such, the relationship between master and vassal among samurai was not absolute. The situation did not change even after the establishment of the Kamakura bakufu (Japanese feudal government headed by a shogun) as the first military government.
As it became the Muromachi period, the relationship between master and vassal among samurai became comparably stronger to earlier times. Many samurai descendants of a Shugo (military governor) during the Kamakura period were appointed to the position again by the Muromachi bakufu. They obtained the authority to impose taxes on shoen based on new systems like hanzei (a system under which Shugo were allowed to collect half of the taxes from shoen) and shugouke (the contract system under which the owner of a shoen entrusted a Shugo to manage their shoen and pay customs). At the same time, they made the descendents of a Jito (military land steward) called Kokujin ryoshu (local samurai) their subordinates, acquired the authority to collect taxes from shoen owned by Ingu oshinke, temples and shrines, and strengthened their power base. A number of Kokujin ryoshu protected themselves from intervention by a Shugo or checked the movements of Shugo by obtaining the status of bakufu hokoshu (a military post of the bakufu). Conversely, some obtained the position of Shugodai (deputy of Shugo), or other official positions by serving the Shugo, through the Shugo or the bakufu. In this case, they protected themselves from outside enemies or justified their ruling authority based on their positions.
On the other hand, strengthening the ruling power of a Shugo or Kokujin was not necessarily accomplished smoothly, due to vassals often changing loyalty to other Shugo or rebelled against a Shugo in an alliance with another Kokujin. In terms of tax collection as well, taxes could not be collected from Shoen after they obtained the right of Shugoshi funyu (a right to reject the entrance of a Shugo) and they had no way to collect money without embezzling illegally. In the case of Kokujin ryoshu, their relationship with clan members, branch families and Dogo under their rule was similar to an alliance, rather than a relationship of master and vassal; in this sense, Kokujin ryoshu were more akin to leaders rather than masters. Kokujin were therefore unable to neglect the intentions of their branch families and Dogo. In some cases, subordinates of Kokujin became independent Kokujin by appealing to the bakufu or the Shugo. When conflict of interests occurred, some branch families went so far as to publicly rebel against the Kokujin and engage in battle. As shown above, the relationship of master and vassal among samurai until the medieval period was based only on the common interests of both parties and was not absolute.
Sengoku daimyo (Japanese territorial lord in the Sengoku period (period of Warring States)) and Kashindan
The importance of common interests in a relationship of master and vassal did not change in the Sengoku period. Rather, it was even more apparent when vassals began changing masters in the event of a serious conflict of interest and Gekokujo (a revolt of vassals against their lords) became a matter of course. The big difference between the Sengoku daimyo and the Shugo daimyo (military governors), Shugodai and Kokujin ryoshu from the Muromachi period, however, was in whether or not they could organize strong Kashindan.
Unlike their counterparts in the medieval period, Sengoku daimyo actively appointed capable vassals to important positions. Generally presiding over the politics of a daimyo family were clan members, branch families, relatives, powerful Kokujin and vassals who were descendants of the Dogo. Within the Kashindan under a Sengoku daimyo, however, there was a trend to give promotions based on abilities; this was seen in the case of Hideyoshi HASHIBA (Hideyoshi TOYOTOMI) who had been born from a peasant family, became an ashigaru (common foot soldier) and was promoted to a vassal by Nobunaga ODA, a Sengoku daimyo in Owari Province. On the other hand, there were also conflicts between hereditary vassals, who held their status based on bloodline or traditional master-vassal relationships, and individuals who were newly appointed due to their abilities.
In the late Sengoku period, powerful Sengoku daimyo brought their vassals into complete subordination, whereas before they had been independent to a certain degree and were able to refuse orders depending on the circumstances. Sengoku daimyo constructed castle towns, giving residences to their vassals and families inside the towns in order to prevent revolts and indigenization. After Hideyoshi TOYOTOMI became a Kanpaku (chief adviser to the Emperor), a policy called heinobunri (separation of warrior class from the soil of its territory) was implemented. As a result of the policy, vassals who had been engaged in agriculture in their territories in times of peace became full-time bureaucrats or warriors. This caused a change in the relationship between vassals and daimyo; whereas vassals formerly went to the castle to work when necessary, under the new policy they were required to work in the castle every day.
Since the Edo period
During the Edo period when the Shogun held absolute authority, relations between Kinsei daimyo (early modern lords), who were Jikishin (great vassals), and their Kashindan, who were Baishin (indirect vassals), became a categorical master-subordinate relationship. Daimyo adopted a horoku (salary) system in place of the chigyo system (a system under which vassals were entitled and given the right to rule the land) and monopolized the right to rule the land. Under these circumstances, the nature of Kashindan changed from a group of ryoshu (feudal lords) to a group of employees serving a daimyo family. As it became a peaceful period, samurai became increasingly bureaucratic, not only due to vassals being given important positions when they excelled in governance instead of in military affairs, but because of the heinobunri policy implemented in the Azuchi-Momoyama period and the adoption of the horoku system in the Edo period as well. This resulted in the nature of samurai changing from ryoshu to bureaucrats and officials.