The truce with the Porte and the conquest of Portugal marked a turning-point in Spanish policy. The greatest danger to Spain was no longer in the Mediterranean but in the Atlantic. France and England were supporting her enemies in the Netherlands and in Portugal. Drake and the English pirates were wickedly and illegally disrupting Spanish trade with her colonies and robbing the king and his subjects. The pope, Cardinal Granvelle and Philip's Spanish advisers were pressing for a more aggressive policy. Gradually, the king himself became convinced that the defence, both of his own interests and of the church, demanded more active Spanish intervention in western Europe.

The immediate occasion for the change in Spanish policy was the death of the duke of Anjou and of the prince of Orange (1584). Even before Anjou's death, the United Provinces (i.e. the members of the Union of Utrecht) had once more approached both Henry III and Elizabeth I with offers of the sovereignty over the Netherlands. Henry III again refused. William's death and the fall of Antwerp made help urgent if the Union was to be saved. On 20 August 1585 Elizabeth therefore, while likewise refusing the sovereignty, agreed to send five thousand troops, under the command of the earl of Leicester, to the Netherlands. Leicester and two other Englishmen were to have seats in the Council of State. Brill and Flushing, commanding the estuaries of the Meuse and the Scheldt, were handed over to the English as bases and as security for the repayment of the English government's expenses. Elizabeth had driven a hard bargain and had still not yet broken completely with Spain. But, for the first time, she was committed to fight Philip II openly and, as it turned out, committed more heavily than she had bargained for.