On 23 December, Vere learned from a deserter that the Spanish were in preparation for a large impending assault on the city; he realized he had no hope except to hold for time. Vere's frustration with the Dutch continued, writing many letters and complaining about the lack of support, in addition he demanded reinforcements. He therefore proposed a parley to the Spaniards for negotiations; but this was a ploy hoping to gain time to await the arrival of the reinforcements. The Spanish accepted and Vere sent two of his captains, John Ogle and Charles Fairfax, as hostages to the Spanish camp, while the Spanish sent in return Mateo Antonio, quartermaster general of the Spanish army, and Matteo Serrano, Governor of Sluis, to negotiate "terms of possible surrender".