The year 1631 was signalized by an expedition into Flanders, consisting of eighteen thousand men, intended against Dunkirk, but hastily abandoned, in spite of every probability of success, by the commissioners of the states-general, who accompanied the army, and thwarted all the ardor and vigor of the Prince of Orange. But another great naval victory in the narrow seas of Zealand recompensed the disappointments of this inglorious affair. The splendid victories of Augustus Adolphus against the imperial arms in Germany changed the whole face of European affairs. Protestantism began once more to raise its head; and the important conquests by Frederick Henry of almost all the strong places on the Meuse, including Maestricht, the strongest of all, gave the United Provinces their ample share in the glories of the war. The death of the archduchess Isabella, which took place at Brussels in the year 1633, added considerably to the difficulties of Spain in the Belgian provinces. The defection of the count of Berg, the chief general of their armies, who was actuated by resentment on the appointment of the marquis of St. Croix over his head, threw everything into confusion, in exposing a widespread confederacy among the nobility of these provinces to erect themselves into an independent republic, strengthened by a perpetual alliance with the United Provinces against the power of Spain. But the plot failed, chiefly, it is said, by the imprudence of the king of England, who let the secret slip, from some motives vaguely hinted at, but never sufficiently explained. After the death of Isabella, the prince of Brabancon was arrested. The prince of Epinoi and the duke of Burnonville made their escape; and the duke of Arschot, who was arrested in Spain, was soon liberated, in consideration of some discoveries into the nature of the plot. An armistice, published in 1634, threw this whole affair into complete oblivion. The king of Spain appointed his brother Ferdinand, a cardinal and archbishop of Toledo, to the dignity of governor-general of the Netherlands. He repaired to Germany at the head of seventeen thousand men, and bore his share in the victory of Nordlingen; after which he hastened to the Netherlands, and made his entry into Brussels in 1634. Richelieu had hitherto only combated the house of Austria in these countries by negotiation and intrigue; but he now entered warmly into the proposals made by Holland for a treaty offensive and defensive between Louis XIII. and the republic. By a treaty soon after concluded (February 8, 1635) the king of France engaged to invade the Belgian provinces with an army of thirty thousand men, in concert with a Dutch force of equal number. It was agreed that if Belgium would consent to break from the Spanish yoke it was to be erected into a free state; if, on the contrary, it would not co-operate for its own freedom, France and Holland were to dismember, and to divide it equally.