Ferdinand’s position changed radically after 1630. What had been a conflict between the princes of the Empire and the emperor now assumed international dimensions, with France and Sweden becoming dangerous enemies for the Habsburgs.
Having endeavoured for generations to break Spain’s superior power, France under the leadership of Cardinal Richelieu seized the opportunity to restrict the emperor’s powers with the support of the Protestant party in the Empire. The cardinal’s long-term aim was to play off the Spanish and Austrian branches of the dynasty against each other, thus undermining the cohesion of the dynasty as a whole.
The greatest threat to Ferdinand’s plans, however, came from the north. The Swedish king Gustav Adolf invaded the Empire in order to support his Protestant brothers in the faith against the emperor’s ‘tyrannical yoke’.
Ferdinand was forced to make concessions to the imperial Estates. One of their demands was the dismissal of the all-powerful imperial commander-in-chief Albrecht Wallenstein, a demand that Ferdinand acceded to at the Diet of the Electors in Regensburg in 1630. The fortunes of war then changed abruptly, with the army of the Catholic League suffering an annihilating defeat at Breitenfeld in 1631. When the troops of the Protestant elector of Saxony occupied Prague and the war began to encroach on Habsburg territory, Ferdinand restored Wallenstein to his position. Although the Swedish troops won a narrow victory in the ensuing battle at Lützen in 1632, King Gustav Adolf was killed and the Protestants lost their charismatic leader.
Soon afterwards Wallenstein began to launch his own, independent initiatives, and his shadowy manoeuvring as commander of the imperial troops made him appear unreliable in the eyes of the Viennese court, which suspected that the imperial generalissimo intended to overthrow the emperor and seize power himself. Following lengthy deliberations in which credence was given to incriminating reports, Ferdinand abandoned his commander-in-chief, whereupon Wallenstein was murdered in the city of Eger (Cheb) in western Bohemia on 25 February 1634. This much-discussed contract killing and Ferdinand’s role in it continue to occupy historians to this day.
Within the Empire willingness to compromise grew on both sides of the religious divide. In the Peace of Prague concluded in 1635 Ferdinand backed down from the demands of the Edict of Restitution and formulated an offer of peace to the Estates of the Empire. This defused the conflict within the Empire subsequently enabling it to unite in driving back its external enemies, Sweden and France.
Ultimately Ferdinand recognized the unfeasibility of imposing religious uniformity within the Empire. At the same time he was also making preparations for his son, likewise called Ferdinand, to succeed him as emperor. One of his final political successes was the acceptance by the electors of his son as Roman-German king and future emperor in December 1636.
At the beginning of 1637 Ferdinand’s health began to deteriorate. The emperor died in Vienna but in accordance with the provisions of his last will he was buried in the mausoleum he had commissioned for himself in Graz.