The Siege of Sluis of 1587 took place between 12 June and 4 August 1587, as part of the Eighty Years' War and the Anglo-Spanish War (1585–1604). On 12 June 1587, Don Alexander Farnese, Duke of Parma (Spanish: Alejandro Farnesio), Governor-General of the Spanish Netherlands, and commander-in-chief of the Army of Flanders, laid siege to the strategic deep-water port of Sluis, defended by English and Dutch troops under Sir Robert Dudley, Earl of Leicester, Governor-General of the United Provinces, and Sir Roger Williams. On 24 June, the bombardment began, and on 4 August, after of 13 days of constant fighting around the walls, the English garrison surrendered. The lost of the English-held port of Sluis revealed the inability of Leicester to assert his authority over the Dutch allies, who refu