Circuits originated in China during the Han dynasty and were used as a lower-tier administrative division, comparable to the county (simplified Chinese: 县; traditional Chinese: 縣; pinyin: xiàn, also translated as "districts"). They were used only in the fringes of the empire, which were either inhabited primarily by non-Han Chinese peoples or too geographically isolated from the rest of the Han centers of power. The system fell into disuse after the collapse of the Western Jin dynasty.
The administrative division was revived in 627 when TangEmperor Taizong made it the highest level administrative division and subdivided China into ten circuits. These were originally meant to be purely geographic and not administrative. Emperor Xuanzong added a further five, and slowly the circuits strengthened their own power until they became powerful regional forces that tore the country apart during the Five Dynasties and Ten Kingdoms period. During the Song and Jin dynasties, circuits (“dao”) were renamed lu (路), both of which mean "road" or "path".
Dao were revived during the Yuan dynasty. Circuits were demoted to the second level after the Yuan dynasty established provinces at the very top and remained there for the next several centuries. The Yuan dynasty also had lu (sometimes translated as "route"), but it was simply the Chinese word used for the Mongolian administrative unit, the cölge. The Yuan lu had little to do with the circuits (lu) in the Song and Jin dynasties and were closer in size to prefectures.[2]
During the Republic of China era, circuits still existed as high-level, though not top-level, administrative divisions such as Qiongya Circuit (now Hainan province). After the Nationalists had successfully reunite China in 1928, all circuits were replaced with committees or simply abandoned. In 1932, administrative circuits (Chinese: 行政督察區; pinyin: xíngzhèng dūchá qū) were reintroduced and lasted until 1949.
During the Asuka period (538–710), Japan was organized into five provinces and seven circuits, known as the Gokishichidō (5 ki 7 dō), as part of a legal and governmental system borrowed from the Chinese.[3] Though these units did not survive as administrative structures beyond the Muromachi period (1336–1573), they did remain important geographical entities until the 19th century. The seven circuits spread over the islands of Honshū, Shikoku, and Kyūshū:
Tōsandō (東山道) "East Mountain Circuit": 13 provinces
In the mid-19th century, the northern island of Ezo was settled, and renamed Hokkaidō (北海道, "North Sea Circuit"). It is currently the only prefecture of Japan named with the dō (circuit) suffix.
