The Battle of Berestechko (Ukrainian: Битва під Берестечком, Polish: Bitwa pod Beresteczkiem; 28 June – 10 July 1651) was fought between the Cossack Hetmanate and Crimean Khanate against the Polish–Lithuanian Commonwealth as a part of the Khmelnytsky Uprising.

Near the site of the present-day city of Berestechko in Ukraine, a forces of the Zaporozhian Cossacks and Crimean Tatars under the command of Hetman Bohdan Khmelnytsky, Otaman Tymofiy Khmelnytsky, Colonels Ivan Bohun and Fylon Dzhalaliy with Khan İslâm III Giray and Tugay Bey, who was killed in the battle, was defeated by the Polish–Lithuanian Commonwealth's forces under the command of the Polish King John II Casimir, Prince Jeremi Wiśniowiecki, Hetmans Marcin Kalinowski and Stanisław Lanckoroński.

One of the senior Polish commanders, Duke Bogusław Radziwiłł, wrote that the Crown Army had 80,000 soldiers,[10] which included "40,000 regulars and 40,000 nobles of the levée en masse, accompanied by roughly the same number of various servants, footmen, and such.

The Registered Cossack force was supported by a large number of Ukrainian peasants armed with scythes, flails and the likes which were rather undisciplined and organised poorly.

During the first day of "skirmishes by the Tatar and Cossack vanguard regiments", the Poles were victorious "since their army sustained that first attack cheerfully and in high spirits".

This time, Tatar cavalry gained the upper hand, pushing the Poles back to their camp but were then "barely repelled" by heavy fire from the Polish infantry and artillery.

The left flank of the Polish army started to retreat when the King reinforced it with all German mercenaries under command of Colonel Houwaldt who repulsed the attack and "drove the Tatars from the field".

With the battle already turning against them, the Tatar forces panicked, "abandoning the Khan's camp as it stood", and fled the battlefield leaving most of their belongings behind.

With the Tatar cavalry gone, the Cossacks moved their wagons in the night to a better defensive position closer to the river, dug trenches and constructed walls to Polish surprise in the morning.

[21] The Cossack morale was decreasing and desertions started to the other river side, though they maintained a high rate of artillery fire and made occasional sorties.

The main Polish force observed the disorder, but didn't launch an attack on the Cossack camp immediately thinking of a trap.

"Khmelnytsky's tent was captured intact, with all his belongings", which included two banners, one he received from John II Casimir's 1649 commission and one from Wladyslaw IV in 1646.

As the battle ended, King John Casimir made the error of not pressing even harder the pursuit of the fleeing Cossacks, "the first several days following ... defeat of the enemy were so blatantly wasted" but there "was the unwillingness of the nobility's levée en masse to proceed into Ukraine" plus "rainy weather and a lack of food and fodder, coupled with epidemics and diseases that were becoming active in the army, were generally undercutting any energy for war".

[26] After making promises of a pecuniary nature, Hetman Bohdan Khmelnytsky was soon released by the Tatar Khan İslâm III Giray He was then able to reassemble the Zaporozhian Host, which was able to present a substantial army to confront the Poles at the Battle of Bila Tserkva (1651).

[27] Samuel Twardowski's narrative poem, The Civil War, describes the setting for the battle along the Styr River:[28] There is a little town on it, In the middle of Volhynia, called Berestechko, Belonging to the Leszczynski family, that was not as famous in the past As it has now become – both ancient Cannae And Khotyn are far outshone by it, because as many heads here Our eyes have seen as at Thermopylae Or Marathon they counted, although there the whole strength Of Europe and Asia had come together.