The Battle of Berestechko (; ) was fought "after a two-year truce", between the Ukrainian Cossacks, led by Hetman Bohdan Khmelnytsky, aided by their Crimean Tatar allies, and a Polish-Lithuanian Commonwealth army under King John II Casimir. Fought over three days from 28 to 30 June 1651, the battle took place in the Polish 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 km away, who's right flank was against the Pliashivka (Pliashova) River and the Tartar army on their left flank. It was, very probably, the world's largest land battle of the 17th century.