The Spanish Netherlands
The King of Hungary tried to convince his cousin to stay and to strengthen their hold on Germany, but the Cardinal-Infante Ferdinand moved his troops almost immediately after the battle to continue to Brussels. At the end of 1634 he entered Brussels with all the glory befitting a Governor-General. Due to the unpopularity of the clergy in Brussels, he downplayed his religious status and instead emphasized his worldly ranks. Ferdinand was a skilled politician and diplomat, and quickly reformed the government and the military. He especially managed to win the support of the Flemings against France. However, his powers were secretly limited, and the leader of his army was instructed to follow Spanish orders instead of Ferdinand's orders if necessary.
In 1635, the French attacked Namur, planning to merge with the Dutch near Maastricht but were held off by well prepared defenses. At the siege of Leuven, the invading Franco-Dutch forces, suffering badly from supply problems and greatly depleted by disease and desertion, were forced to withdraw when a Spanish relief force arrived. This allowed Spanish forces under Ferdinand to go on the offensive. The Dutch were driven back and the French retreated. Ferdinand subsequently was able to capture Diest, Goch, Gennep, Limbourg, and Schenkenschanz.
"France declared war on me (on me, not on my brother Philip) and I've since then had to fight against their armies and the intrigues of our brother-in-law Louis and his relentless minister Richelieu." – Cardinal-Infante Ferdinand
In 1636, Ferdinand disempowered the last Protestant priests in the Spanish Netherlands, and continued his military counter-offensive by capturing Hirson, Le Catelet, and La Capelle, and securing Luxembourg using the usual mixed nationalities typical of the early modern age that included Croatian troops, and reaching as far a stronghold in France as Corbie during the Crossing of the Somme, threatening Paris.
In 1637, with Spanish forces concentrated in the fight with the French, a relatively lightly defended Breda, that had been under Spanish control for twelve years, was recaptured by the Dutch after a 3-month siege by the Prince of Orange. The loss of Breda was a blow to Spanish prestige but was of much less strategic significance than the gains made by Ferdinand during its course in taking the Dutch towns of Venlo and Roermond in the Meuse valley, effectively cutting Maastricht from the Dutch Republic and, thus, preventing further Dutch attacks on the Spanish Netherlands from the east. In the southern front Ferdinand lost the towns of La Capelle, Landrecies, and Damvillers to the French, but then he forced them to retreat south of Maubeuge.
In 1638, Ferdinand's army successfully defended Antwerp, Saint-Omer and Geldern from the Dutch and French armies. His defense of Antwerp led to the Battle of Kallo, where Ferdinand achieved a crushing victory over the Dutch army while heavily outnumbered. In a letter to his brother the King of Spain shortly afterwards, Ferdinand described the battle as "the greatest victory which your Majesty's arms have achieved since the war in the Low Countries began".
In 1639, Ferdinand managed again to thwart Franco-Dutch plans. The Dutch navy destroyed an important Spanish fleet in the Battle of the Downs, off the English coast, but it failed to prevent most of the army it was carrying, some 7,000 to 10,500 infantry, from landing at Dunkirk. While Ferdinand frustrated the Prince of Orange's move against Hulst, an Imperial-Spanish army under Count Piccolomini destroyed the main French army in the south at the Battle of Thionville.
In 1640, Dutch attacks on Hulst and Bruges were repelled by the local Spanish garrisons under the Cardinal-Infante. In the south, after a failed attack on the Spanish fortress of Charlemont in Givet, a combined Dutch and French army under Gaspard III de Coligny and Frederick Henry launched a great offensive upon Arras, the capital of the County of Artois. The city finally surrendered on 9 August, marking the first victory of importance for the French in the war after five years of fighting.
