During the Second World War, the basic combat unit of the Ukrainian Insurgent Army (UPA) was a kurin. At some point in time in Ukraine kurin used to mean a village and also used to stand for the 11th lowest Cossack rank.
In Zaporizhian Host it was an administrative-military unit equivalent to a battalion of four to eight hundred members, divided into three or four sotnias. The Otamans of kurins constituted the Kosh of the Host which was chaired by the Kosh Otaman. There were 38 kurins of the Zaporizhian Host. After the kurins were transferred to Kuban two more were added.
In Cossack Hetmanate, kurin was part of a sotnia consisting of 10 to 40 Cossacks.
Memories of a Zaporozhets. ... There were 40 thousand of them, they were divided into 40 kurens, or villages, each with 100 houses. This people, made up of representatives of various neighboring nations, lived on the banks of the Dnieper opposite the rapids and from there settled along the vast steppes to the left of Ingulets. They considered it an honor to live single, and their laws forbade them to live with women, so they did not meet the latter among them. Any fugitive from Turkey, Greece, Poland, Russia found shelter with them and could enroll in the Cossacks, if only he obeyed their laws. ... - Gilbert Romm. Travel to the Crimea in 1786 - Leningrad: Edition of the Leningrad State University, 1941. - 79 p. The Zaporozhye Kosh (that is, in fact, the Sich) primordially (that is, no one remembers from what time)  consisted of 38 kurens, ruled by kuren chieftains.
The names of the kurens were mainly given in memory of the cities and villages from which the first Cossacks came to Zaporozhye, who laid the kuren, in the area from which the Cossacks of this kuren traditionally originated (Poltava, Umansky, Kanevsky, Korsunsky, Baturinsky, etc.), some of the kurens were named after some famous kuren comrade or the first kuren ataman .
Each person accepted into the Cossacks entered a certain kuren. The kurens consisted only of "comradeship", that is, single Cossacks who had the right to live in the Sich, while married people lived in palanquets and were considered "citizenship" .
Each kuren had its own farm.
When the Zaporizhzhya Army set out on a campaign by land, it was divided not into smokes, but into shelves (palanquets) so that the regiment consisted of three and four kuren Cossacks.
At the head of the kuren was the ataman. Ataman was elected by the kurennaya Cossack council - kurennaya council. Kurennaya Rada had broad military-administrative competencies and decided some court cases. The kurenniy ataman kept the kurens 'treasury, was responsible for providing the kurens with fuel and food, kept the kurens' lists, monitored the movement of the Cossacks .
On January 1 of each year, the Sechevaya Rada was convened in the Sich, in which all the Cossacks participated with the same rights. Before that, at the kurenna council, each kuren chose a kuren ataman and a cook for the whole year, and after that all kurens together chose a koshevoy ataman, a military judge, a clerk and esaul and even older ones: treasurer, gunner, dovbysh, cornet, bunchuzhny and other government officials ...
- p.il, Mikaberidze, Aleksander, The Russian officer Corps in the Revolutionary and Napoleonic Wars, Savas Beatie, New York, 2005