The Battle of Berestechko was fought between the Ukrainian Cossacks, led by Hetman Bohdan Khmelnytsky, aided by their Crimean Tatar allies, and a Polish army under King John II Casimir. It was a battle of a Cossack rebellion in Ukraine that took place in the years 1648–1657 after the expiration of a two-year truce. Fought from 28 to 30 June 1651, the battle took place in the province of Volhynia, on the hilly plain south of the Styr River. The Polish camp was on the river opposite Berestechko and faced south, towards the Cossack army about two kilometers away, whose right flank was against the River Pliashivka (Pliashova) and the Tatar army on their left flank. It was probably the largest European land battle of the 17th century.
John III Sobieski was promoted to the rank of pułkownik and fought with distinction in the Battle of Berestechko.