The outset of Sir Horace's individual career in the Dutch States Army was marked by the fall of Ostend on 24 September 1604 to the Spanish general, Ambrosio Spinola. As a makeweight to Ostend, Maurice of Nassau, Prince of Orange meditated the recapture of Sluys. The Spanish general opposed the advance upon the town with a force of two thousand men strongly entrenched at Damme, situated between Sluys and Bruges. This force, under the Spanish general of horse, Don Luis de Velasco, had to be dislodged, a risky operation. Vere won for his command the approbation of the States-General. In July 1604 Spinola was foiled in an attempt to relieve the town, and on 20 August it was surrendered.