The rank was first introduced in the armies of the Commonwealth in the 17th century to denote a captain (rotmistrz) of the core banner of a regiment. By the end of the 17th century, the title of the assignment became a de facto rank as such and started to denote the commanding officer of the entire regiment. In mercenary troops fighting in the ranks of the Polish–Lithuanian Commonwealth's army, the direct equivalent of the rank of pułkownik was oberszter, but in the 18th century the rank was abolished and renamed as pułkownik as well. Interwar During the Sanation in the period between World War I and World War II, a large number of officers were promoted to the rank, often for political reasons (the rule of the Sanation was even dubbed the government of the colonels because of that). World War II During the Invasion of Poland in 1939, the Polish divisions were commanded by officers of many grades, from colonels to three-star generals. In fact 22 divisions out of 42 were commanded by colonels in 1939. The pułkownicy (plural of pułkownik) also commanded units of all sizes, from divisions down to mere battalions. Ukraine In the Zaporozhian Host, the political, social, and military organization of Ukrainian cossacks, the title polkovnyk indicated a high military rank among the Ukrainian Cossack starshyna (officers); a polkovnyk commanded one or more military detachments during land and naval military actions in the 16th to 18th centuries. In the 18th century, a polkovnyk was a leader of a palanka, a territorial unit of the Zaporozhian Host. The military council elected a palanka polkovnyk to serve for a term of one year. He represented the Kosh Otaman in the palanka and had significant powers, including the right to condemn Cossacks to the death penalty. At the time of liquidation of the Zaporozhian Host by the Russian government in 1775, there were eight palanka polkovnyks. As symbol of office a polkovnyk wore a pernach (a mace with a hexagonal head; see also bulawa) in his belt. In the Registered Cossack Army of the Polish–Lithuanian Commonwealth in the 16th and 17th centuries, a polkovnyk commanded a regiment (. polk), a Cossack military unit. After the reform of the Cossack army by hetman Mykhailo Doroshenko in the 1620s there were six Cossack regiments, each comprising one thousand Cossacks. Polkovnyks were elected by the Cossack Council (, rada) subject to