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[[File:Iyo-matsuyama-sankin.JPG|center|thumb|800px|Detail from a handscroll painting depicting the ''sankin kôtai'' procession of the lord of [[Iyo-Matsuyama han]]. Date unknown. [[National Museum of Japanese History]]]]

[[File:Iyo-matsuyama-sankin.JPG|center|thumb|800px|Detail from a handscroll painting depicting the ''sankin kôtai'' procession of the lord of [[Iyo-Matsuyama han]]. Date unknown. [[National Museum of Japanese History]]]]

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, alternating with his father, so that either the lord or his heir would be in Edo at any given time. Retired ''daimyô'' were also obliged to travel to Edo occasionally, to be re-confirmed in their being granted leave to remain in their domain (or in Edo, as they wished).<ref name=nagairei>Nagai Hiroshi 永井博, ''Sankin kôtai to daimyô gyôretsu'' 参勤交代と大名行列 (Tokyo: Yôsensha 洋泉社 MOOK, 2012), 126-131.</ref>

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, alternating with his father, so that either the lord or his heir would be in Edo at any given time. At some point after that, it became standard for the heir to simply be raised in Edo, and not to travel to the home domain (''kunimoto'') until he succeeded his father and became ''daimyô''; this further served the Tokugawa purposes of weakening ''daimyô'' ties to their power bases, as it meant that most ''daimyô'', having been raised in Edo, had little familiarity with their domain and its people. The first entry of a new ''daimyô'' into the domain, an event known as ''okuni iri'', was thus heightened in significance, and was often accompanied by great celebrations, and commemorated in paintings or other works.<ref>''Edo-zu byôbu to gyôretsu'', exhibition pamphlet, National Museum of Japanese History, August 2014.</ref> Retired ''daimyô'' were also obliged to travel to Edo occasionally, to be re-confirmed in their being granted leave to remain in their domain (or in Edo, as they wished).<ref name=nagairei>Nagai Hiroshi 永井博, ''Sankin kôtai to daimyô gyôretsu'' 参勤交代と大名行列 (Tokyo: Yôsensha 洋泉社 MOOK, 2012), 126-131.</ref>

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 [[Tsushima han]] which governed relations and trade with [[Joseon|Korea]], and [[Fukuoka han|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.<ref>[[Mark Ravina]], ''Land and Lordship in Early Modern Japan'', Stanford University Press (1999), 152.</ref> ''Daimyô'' could also request, and be granted, exceptions from ''sankin kôtai'' on a one-time basis, when the lord was ill or the Edo mansion had burned down, or when the domain was fulfilling its obligations to the shogunate through corvée contributions to public works that year.<ref name=nagairei/>

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 [[Tsushima han]] which governed relations and trade with [[Joseon|Korea]], and [[Fukuoka han|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.<ref>[[Mark Ravina]], ''Land and Lordship in Early Modern Japan'', Stanford University Press (1999), 152.</ref> ''Daimyô'' could also request, and be granted, exceptions from ''sankin kôtai'' on a one-time basis, when the lord was ill or the Edo mansion had burned down, or when the domain was fulfilling its obligations to the shogunate through corvée contributions to public works that year.<ref name=nagairei/>