Sankin kotai

• Japanese: 参勤交代 (sankin koutai)

Sankin kôtai, or "alternate attendance," was a system of military service which served as a central piece of the Tokugawa shogunate's systems for controlling the daimyô and maintaining power. Daimyô were obligated to alternate their residence between Edo and their domain; the expense of journeys to and from Edo each other year, with large entourages, combined with the expense of maintaining mansions in Edo often cost significant portions of the domain's resources, keeping them from consolidating power within their domains. The process of having so many samurai traveling to and from the capital, and maintaining residences in the capital, had a profound effect on cultural diffusion throughout the realm, and contributed significantly to the samurai-heavy demographic character of Edo.

Initially voluntary, the system was made mandatory for tozama daimyô in 1635 in a re-issuance of the buke shohatto ("various laws for warrior families"); this was expanded to all daimyô in 1642. Lords were obligated to maintain a residence in Edo, where members of their close family would reside as hostages against the daimyô's disobedience or rebellion. As of 1648, each lord's heir was obligated to travel to Edo as well, and from 1684 onwards, the fudai daimyô had to make their sankin journeys every six months. Though most daimyô were obliged to perform this journey regularly, some tozama daimyô were granted exceptions, in most cases due to their great service to the realm in other respects, or after successfully arguing for the excessiveness of the burden. These included Satsuma han, which was particularly powerful and had a particularly lengthy journey; Tsushima han which governed relations and trade with Korea; and Fukuoka and Saga han, which contributed to the defense of the port of Nagasaki. Some northern domains which contributed to responses to Russian incursions also received temporary exemptions at times.

The sankin kôtai system ensured a reliable flow of considerable numbers of elite travelers across the country, contributing considerably to both official and private construction of post-stations and inns (and their surrounding towns), lighthouses and port facilities, maintenance of highways, and expansion of travel-related services, such as networks of messengers, porters, and horses. Corvée labor was employed to provide a considerable portion of the porters, boatmen, and the like. Barrier checkpoints called sekisho were established along the highways to regulate travel; among their functions, too, was to enforce that firearms not be carried into Edo (so as to help prevent rebellion), and that women (who might be hostage members of daimyô families) not be allowed to leave.

Many daimyô of western Japan also came to maintain mansions in Osaka and Kyoto as well, where the daimyô and his retinue would stay during their journeys to and from the shogun's capital, thus contributing to the culture and economy of these cities as well.

In the early Edo period, most daimyô of Kyushu, Shikoku, and western Honshû, traveled by ship to Osaka; sekibune were converted into luxurious gozabune for this portion of the journey, and riverboats were used to travel up the Yodo River from Osaka to Fushimi, from which the daimyô would then travel overland to Kyoto proper, and then along the Tôkaidô to Edo. Later on, however, many daimyô switched to traveling overland for as much of the journey as they could, avoiding sea travel. The Shimazu clan lords of Satsuma han likely had the longest journey; it typically took 40 to 60 days to travel the 440 ri to Edo. Though they originally sailed to Osaka from Kumisaki (Satsuma Sendai) or Wakimoto (Akune) on Kyushu's west coast, or from Hososhima in Hyûga province on Kyushu's east coast, they later switched to marching overland across Kyushu to Shimonoseki, and then walking the San'yôdô to Osaka.

The financial costs of sankin kôtai were among the heaviest burdens upon daimyô budgets, leading to many daimyô incurring very significant debts over the course of the period. Despite the expense, however, daimyô often felt obligated to maintain large entourages and lavish traveling conditions in order to maintain impressions of their power and prestige; not only the number of men in one's entourage, but the number of spears preceding and following the daimyô in procession, the number of certain types of baskets and baggage, among other elements of performance and display, meant a lot in terms of representing one's prestige and power to all those who could see it. For this reason, though the shogunate repeatedly tried to restrict the allowable size of sankin kôtai entourages, daimyô regularly exceeded the official limits.

The sankin kôtai system came gradually to an end in the Bakumatsu period. Obligations were relaxed in 1862, leading to a great many samurai leaving the city.