Registered Cossacks (, , ) comprised special Cossack units of the Polish–Lithuanian Commonwealth army in the 16th and 17th centuries. Registered Cossacks became a military formation of the Commonwealth army beginning in 1572 soon after the Union of Lublin (1569), when most of the territory of modern Ukraine passed to the Crown of Poland. Registered Cossack formations were based on the Zaporozhian Cossacks who already lived on the lower reaches of the Dnieper River amidst the Pontic steppes as well as on self-defense formations within settlements in the region of modern Central and Southern Ukraine. History Origins The first recorded official plan for enlisting Cossack formations as a border service in Poland-Lithuania was brought to the State Council of the Grand Duchy of Lithuania in 1524 by Semen Polozovic and Kristof Kmitic. However, due to a lack of funds, the idea was not realized. The starosta of Cherkasy, Ostap Dashkevych, revived the idea at the 1533 council in Piotrków Trybunalski. Dashkevych tried to show that in order to protect the borders beyond the Dnieper River it would be necessary to maintain an army of 2,000 soldiers and several hundred cavalrymen. He pointed out the importance of establishing forts on the river's islands to keep Tatar raids in check. On July 21, 1541 the King of Poland and Grand Duke of Lithuania, Sigismund I the Old, issued an edict to the starosta of Cherkasy, Andrei Glebovich Pronsky (?-1557, a descendant of the Pronsk princes), in which he strictly warned Pronsky to control the Cossack raids against Tatar uluses. With the start of the Livonian War of 1558–1583, the voivode of Kiev, Konstanty Wasyl Ostrogski, and the starosta of Cherkasy, Alexander Wiśniowecki, recruited Cossacks into their armies, while in 1568 King and Grand Duke Sigismund II Augustus sent a proposition to the Zaporizhian Sich to join his foreign campaign and to sign up for royal service. Sigismund II Augustus decreed the formation of registered Cossacks on June 5, 1572 when the King confirmed the orders of Great Crown Hetman Jerzy Jazłowiecki, the voivode of Podole and Ruthenia, for state service. The first commander, called starszy ("elder") of the registered cossacks, was . The registered Cossacks were the only military Cossack formation recognized by the Polish–Lithuanian Commonwealth. Batory and Wars in Livonia, Moldavia and Muscovy The most well-known of the first recorded Cossack reforms came from King of Poland and Grand Duke of