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 The Lowlands. 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 did not compensate for his lack of statesmanlike qualities. In Farnese, whether by good fortune or deliberate choice, he had at length found a consummate general who was to prove himself a match even for William the Silent in all the arts of political combination and intrigue.
At Gembloux, January 31, Don John and Parma fell upon the levies of the States and gained a complete and almost bloodless victory. Had Philip supplied his governor-general with the money he asked for, Don John might now have conquered the whole of the southern Netherlands, but without funds he could achieve little.
Meanwhile all was confusion. The States-General withdrew from Brussels to Antwerp; and William, finding that Matthias was useless, began negotiations with France, England and Germany in the hope of finding in this emergency some other foreign prince ready to brave the wrath of Philip by accepting the suzerainty of the Netherlands.
The Duke of Anjou, brother of the French king, was the favoured candidate of the Catholic party; and William, whose one aim was to secure the aid of a powerful protector in the struggle against Spain, was ready to accept him. Anjou at the head of an army of 15,000 men crossed the frontier at Mons, July 12; and, on the following August 13, a treaty was agreed upon between him and the States-General, by which the French duke, with the title of Defender of the Liberties of the Netherlands, undertook to help the States to expel the Spaniards from the Low Countries. But, to add to the complications of the situation, a German force under the command of John Casimir, brother of the Elector Palatine, and in the pay of Queen Elizabeth, invaded the hapless provinces from the east.
The advent of John Casimir was greeted with enthusiasm by the Calvinist party; and it required all the skill and sagacity of the Prince of Orange to keep the peace and prevent the rival interests from breaking out into open strife in the face of the common enemy. But Don John was helpless, his repeated appeals for financial help remained unanswered, and, sick at heart and weary of life, he contracted a fever and died in his camp at Namur, October 1, 1578. His successor in the governor-generalship was Alexander of Parma, who had now before him a splendid field for the exercise of his great abilities.
The remainder of the year 1578 saw a violent recrudescence of religious bitterness. In vain did Orange, who throughout his later life was a genuine and earnest advocate of religious toleration, strive to the utmost of his powers and with untiring patience to allay the suspicions and fears of the zealots. John Casimir at Ghent, in the fervour of his fanatical Calvinism, committed acts of violence and oppression, which had the very worst effect in the Walloon provinces. In this part of the Netherlands Catholicism was dominant; and there had always been in the provinces of Hainault, Artois, and in the southern districts generally, a feeling of distrust towards Orange. The upholding of the principle of religious toleration by a man who had twice changed his faith was itself suspect; and Farnese left no means untried for increasing this growing anti-Orange feeling among the Catholic nobles.
A party was formed, which bore the name of "The Malcontents," whose leaders were Montigny, Lalaing and La Motte. With these the governor-general entered into negotiations, with the result that an alliance was made between Hainault, Artois, Lille, Douay and Orchies (January 6, 1579), called the Union of Arras, for the maintenance of the Catholic faith, by which these Walloon provinces and towns expressed their readiness to submit to the king on condition that he were willing to agree to uphold their rights and privileges in accordance with the provisions of the Pacification of Ghent.
The Union of Arras did not as yet mean a complete reconciliation with the Spanish sovereign, but it did mean the beginning of a breach between the Calvinist north and the Catholic south, which the statecraft of Parma gradually widened into an impossible chasm. Before this took place, Anjou, Matthias and John Casimir had alike withdrawn from the scene of anarchic confusion, in which for a brief time each had been trying to compass his own ambitious ends in selfish indifference to the welfare of the people they were proposing to deliver from the Spanish yoke. The opening of the year 1579 saw Orange and Parma face to face preparing to measure their strength in a grim struggle for the mastery.