Petro Konashevych-Sahaidachny was a Ukrainian political and civic leader, Hetman of Ukrainian Zaporozhian Cossacks from 1616 to 1622, a brilliant military leader of Polish–Lithuanian Commonwealth both on land and sea. While being a Cossack Hetman, he transformed the Cossack Host from the erratic military formation into regular army. Under his leadership the cossacks, the Orthodox clergy and peasants had been begun to emerge as the united nation. His troops played a significant role in the Battle of Khotyn against the Turks in 1621 and prince Władysław's attempt to gain the Muscovy throne in 1618.