The Thirty Years’ War (1618–1648) marked a crucial period of Habsburg ambitions and overreach, primarily under the rule of Emperor Ferdinand II (1619–1637) and later his son, Ferdinand III (1637–1657). Ferdinand II’s ascension brought a wave of fervent Catholic reform, sparking intense conflicts aimed at reversing Protestantism not only in the Habsburg hereditary lands but across the Holy Roman Empire. His rigid policies, including the 1629 Edict of Restitution, sought to restore Catholic dominance and reclaim properties lost since the 1555 Peace of Augsburg. However, these uncompromising measures escalated tensions across Europe, turning an internal conflict into a continent-wide war.
Ferdinand’s policies led to severe backlash, notably igniting the Bohemian Revolt in 1618 and creating a polarized struggle that soon drew in Denmark, Sweden, and France on the Protestant side, each with their own interests. Early Catholic victories bolstered Ferdinand's confidence, prompting severe crackdowns such as the Frankenburg Lottery, the suppression of the Peasants' Revolt in 1626, and the devastation of Magdeburg in 1631. These harsh tactics intensified Protestant resistance and prolonged the war, ultimately compromising the Habsburg aim of reasserting control over the Empire. By 1635, internal conflicts and intervention by foreign powers made Habsburg aims of religious and political dominance impossible to realize.
When Ferdinand II died in 1637, his son Ferdinand III, a more pragmatic leader, inherited a declining war effort. Known for his support of peace efforts, he oversaw the Peace of Prague in 1635 and, ultimately, the Peace of Westphalia in 1648. This treaty effectively ended the Thirty Years’ War, securing peace in Europe but dealing a blow to Habsburg influence. The treaty gave substantial autonomy to German states, drastically curtailing imperial power and setting a precedent for the sovereignty of European states. This shift in balance ended any realistic hope for Habsburg hegemony, diminishing the Holy Roman Emperor’s influence over central Europe.
The war left an indelible mark on the Habsburg territories. While Ferdinand II’s anti-Protestant campaigns had successfully enforced Catholicism across Austria, Bohemia, and other territories, his absolutist methods alienated subjects and led to demographic and economic decline. The destruction caused by the constant military campaigns and the relentless movement of mercenary armies devastated the population, resulting in significant loss of life—particularly in the German states, where civilian death rates may have reached 50%. The relentless foraging, food shortages, and widespread disease created lasting hardship, deepening the social and economic rifts left by the war.
After the war, Austria emerged under a strengthened Baroque Catholic monarchy that symbolized Habsburg authority and church-state unity, though at great cost. Austrian culture, language, and institutions were reshaped in a German-Catholic image, suppressing Bohemian and Czech traditions. Nevertheless, Austria faced weakened finances and demography, and this, combined with the erosion of central power within the Holy Roman Empire, prevented Austria from becoming a dominant European force, despite its strengthened hold over its own lands. The Treaty of Westphalia marked a new political landscape that would define European politics for centuries, with the Habsburgs increasingly focused on their internal domains rather than universal rule.