Districts of Japan (郡#日本の郡) were areas of traditional local government in Japan before the Meiji period. The function of districts has changed over time, but they continue to exist in contemporary Japan.
Districts are not all the same size. They are roughly equivalent to a county in the United Kingdom or the United States. They are smaller than prefectures and larger than towns and villages.
The counties were originally called kōri and as such had ancient origins in Japan. Although the Nihonshoki claims they were established during the Taika reforms, kōri was originally written as 評. It was not until the Taihō Codex that kōri came into use in the form 郡, which denoted commanders (jùn) in China. Under the Taihō Code, the hierarchy of administrative units was: Province (国, kuni), county kōri, and below that the village (里 or 郷, sato).
Etymologically, the spoken words gun and kuni are related or were adopted into Japanese at different times from different language stages of Chinese - Middle Chinese and Old Chinese. Kōri (pronounced kopori in Old Japanese) is also a loanword, here from Baekje Korean.
Provinces and districts were increasingly irrelevant as administrative units from the Middle Ages onwards, but were used as the primary geographical division of the country - largely static and territorially compact, apart from individual adjustments - in contrast to the political feudal/prefecture division throughout until the late 19th/early 20th century, with the districts also being temporarily revived formally in 1878 as administrative units to subdivide the prefectures.
During the modernization of the administration in the Meiji period according to Western models, the counties were reorganized in 1878 and 1890 according to the model of Prussian districts (engl. "Bezirk" or "district") and received county administrations appointed by the Ministry of the Interior and indirectly elected county assemblies (gunkai). In order to strengthen the local self-government of the municipalities with their elected institutions, the abolition of the counties was decided in 1921 under the Hara cabinet - the dissolution of the county councils and administrations followed a few years later. Hara, a party politician, had already pushed for abolition in the 1900s: While the county chiefs appointed by the Ministry of the Interior were close to the supporters of the party opponent Yamagata Aritomo, the municipal institutions were a stronghold of the bourgeois parties.
As a geographical and statistical unit, guns have outlived their formal abolition. They are still used today in the Japanese address system to indicate the location of towns and villages. Electoral district divisions for prefectural parliaments also follow county boundaries in many places to this day. At the same time, the composition of counties continues today: If a [historically county] town or village municipality becomes part of or itself becomes an -shi (county-free town), it is no longer included in the county. As a result of the major territorial reforms since World War II, in which the number of -shi almost quadrupled by the early 21st century, many counties have disappeared from the map altogether in this way or have been reduced to individual municipalities.
