The Shimazu exercised their influence to exact from the shogunate a number of special exceptions. Satsuma was granted an exception to the shogunate's limit of one castle per domain, a policy which was meant to restrict the military strength of the domains; the Shimazu then formed sub-fiefs within their domain, and doled out castles to their vassals, administering the domain in a manner not unlike a mini-shogunate. They also received special exceptions from the shogunate in regard to the policy of "sankin-kōtai", another policy meant to restrict the wealth and power of the daimyō. Under this policy, every feudal lord was mandated to travel to Edo at least once a year, and to spend some portion of the year there, away from his domain and his power base. The Shimazu were granted permission to make this journey only once every two years. These exceptions thus allowed Satsuma to gain even more power and wealth relative to the majority of other domains.