The position of Leicester was shaken also by his inability to relieve Sluis, which important seaport fell after a long siege into Parma's hands, August 5.

Its capture was attributed by rumour, which in this case had no foundation, to the treachery of the English governor and garrison.

Moreover it was discovered that for some months secret peace negotiations had been passing between the English government and Parma; and this aroused violent suspicions that the Netherlands were merely being used as pawns in English policy, and alienated from the governor-general the sympathy of the preachers, who had been his strongest supporters.

Humiliated and broken in spirit, Leicester, after many bickerings and recriminations, finally left the Netherlands (December 10), though his formal resignation of his post did not reach the States-General until the following April.

Lord Willoughby was placed in command of the English troops.
The year 1588 was the beginning of a decade full of fate for the Dutch Republic.