The position of William at Brussels after his triumphant entry, September 23, 1577, was by no means an easy one.  His main support was derived from a self-elected Council of Eighteen, containing representatives of the gilds and of the citizens.  This Council controlled an armed municipal force and was really master in the city.  In these circumstances the States-General did not venture upon any opposition to the popular wishes, in other words to William, whose influence with the masses was unbounded.  The States-General, therefore, under pressure from the Eighteen, informed Don John, October 8, that they no longer recognised him as governor-general; and the Estates of Brabant appointed the prince to the office of Ruward or governor of the province.  Meanwhile a fresh factor of disturbance had been introduced into the troubled scene.  Certain of the Catholic nobles opposed to Spanish rule, but suspicious of Orange, had invited the twenty year old Archduke Matthias, brother of the emperor, to accept the sovereignty of the Netherlands.  Matthias, who was of an adventurous spirit, after some parleying agreed.  He accordingly left Vienna secretly, and at the end of October arrived in the Netherlands.  Not content with this counter-stroke, Aerschot went to Ghent to stir up opposition to the appointment of William as Ruward of Brabant.  The populace however in Ghent was Orangist, and, rising in revolt, seized Aerschot and a number of other Catholic leaders and threw them into prison.  They were speedily released, but the breach between the Catholic nobles and the Calvinist stadholder of Holland was widened.  William himself saw in the coming of Matthias a favourable opportunity for securing the erection of the Netherlands into a constitutional State under the nominal rule of a Habsburg prince.  By his influence, therefore, the States-General entered into negotiations with the Archduke; and Matthias finally was recognised (December 8) as governor on condition that he accepted the Union of Brussels, He was also induced to place the real power in the hands of Orange with the title of Lieutenant-General.  Matthias made his state entry into Brussels, January 18, 1578.  His position appeared to be strengthened by a treaty concluded with the English queen (January 7) by which Elizabeth promised to send over a body of troops and to grant a subsidy to the States, for the repayment of which the towns of Middelburg, Bruges and Gravelines were to be pledges.

The news however of the step taken by Matthias had had more effect upon Philip II than the despairing appeals of his half-brother.  A powerful army of tried Spanish and Italian troops under the command of Alexander Farnese, Prince of Parma, son of the former regent Margaret, was sent to Flanders.  Farnese was Don John’s nephew, and they had been brought up together at Madrid, being almost of the same age.  Already Philip had determined to replace Don John, whose brilliance as a leader in the field