The Siege of Berestye Fortress occurred in June 1655 when the Polish hetman Jan Sobieski captured Berestye Fortress (Brest, Belarus) from the Swedes amid the Deluge.
In the early months of 1655, King Charles X Gustav of Sweden's armies overran the Grand Duchy of Lithuania's lands in present-day Lithuania and Belarus and threatened Warsaw itself after capturing Berestye Fortress 128 miles to the east. However, King Jan II Casimir of Poland-Lithuania and his generals led a spirited fightback in May-June 1655 after making peace with the Tsardom of Russia and the Cossack Hetmanate, retaking Lublin and Minsk. Having previously defeated several Swedish reinforcement armies moving to bolster Berestye's defenses, Jan Casimir and his armies besieged Berestye on 28 June 1655. The Poles not only faced a small garrison but also Otto Standbok's army, which took shelter within Berestye's wooden walls.
The Poles advanced on the walls with scaling ladders, but the Swedes raked them with gunfire and killed dozens. When the Poles finally made it to the fortress walls, they engaged in ferocious hand-to-hand fighting with the Swedish musketeers manning their positions. Even after the walls were taken, the rest of the Swedish army formed up in the town square. The Swedes again fired on the advancing Poles, inflicting further casualties, but the Swedish musketeers were overpowered by the Poles at close range and the fortress was taken with heavy Polish losses.