Bohun was born in Ukrainian-Ruthenian nobility family. He took part in the Khmelnytsky Uprising against Polish rule in Ukraine. In June 1651 he was elected colonel of troops of Bracław and took part in the Battle of Berestechko against Polish troops led by King John II Casimir, which the Cossacks lost. Surviving the defeat he regathered his forces and in June 1652 took part in the battle of Batih. In this instance the Cossacks were successful; the Polish commander Marcin Kalinowski was killed and the future hetman Stefan Czarniecki barely escaped with his life. The Polish defeat was complete and allowed the Cossack forces to start a successful offensive and effectively gain control over large parts of Ukraine. Until 1657 Ivan Bohun also led his forces in minor skirmishes against Polish forces, notably at Bratslav and Uman. He also fought against the Crimean Tatars who had switched sides in the effect of the Treaty of Zboriv of 1649 (they were initially allied with the Cossacks but supported the Commonwealth in later year).