Refinement of the sankin-kōtai system

Timeline

1. 1635–1641Edo · KantōBefore Iemitsu's reign, daimyō had already been required to regularly attend Edo, but details such as frequency and hostage requirements were not yet fully standardized, and compliance varied among daimyō across regions.
2. 1642Edo · KantōThe shogunate further stipulated that daimyō must regularly attend Edo according to rank, with wives and heirs residing permanently in Edo as hostages, while daimyō alternated residence between their domains and Edo.
3. 1642–1650All of Japan · JapanSankin-kōtai consumed enormous sums from daimyō, weakening their independent military and political capabilities, while simultaneously promoting Edo's prosperity and the development of a nationwide transportation network, becoming a core mechanism for the stable functioning of the han-shogunate system.