The Thirty Years War witnessed the culminatory struggle between the Catholic and centralization-minded emperors, long successively elected from the Austrian ruling house of Habsburg, and the secular territorial princes, mainly Lutheran Protestants but including Calvinists and certain Catholics (as in Bavaria) jealous of their dynastic independence. The princes sought to protect their “liberty” [Libertät] from imperial encroachments and promote the devolution of governmental power within the Empire into their hands. This process had been occurring for centuries, but after the Protestant Reformation, the Austrian emperors attempted to reverse it in the name of Catholic orthodoxy and their own great-power interests, tied also to those of Spain, where a collateral Habsburg lineage reigned. In the Thirty Years War, Swedish and French armed intervention on behalf of the German territorial princes defeated the Austrian emperors’ nearly-attained project, whose realization would have changed the face of German and European history.
The 1648 Peace of Westphalia restructured the institutions of the Empire to definitively block unilateral imperial power. The emperors could attain no innovations without the Imperial Diet or Reichstag’s consent. As of 1792, after various intervening changes, this body seated deputies of eight electoral principalities (Council of Electors), sixty-three deputies representing two hundred and ninety-nine other secular principalities (Secular Bench), thirty-five delegates from the Empire’s self-governing ecclesiastical territories (Ecclesiastical Bench), and fifty-one from the self-governing imperial cities (Council of Cities). New legislation still required majorities in each of these three categories. When innovations touched on religion, the deputies regrouped as representatives of one of the above-mentioned three principal Christian confessions whose practice the war’s outcome had guaranteed (within some limits of toleration) in Germany.
Before the Empire’s demise in 1806, the Reichstag – meeting continually since 1663 on the Danube’s banks in the mixed Protestant-Catholic imperial city of Regensburg – promulgated exceedingly few important new laws. But the emperors retained an influential function in presiding over the organs of imperial justice, to which the hundreds of minor territorial rulers and the nearly 1,500 imperial knights – landed nobility owing allegiance directly to the emperors alone – frequently turned for resolution of internal and external conflicts. The stronger German states (notably Bavaria, Prussia, and Saxony) resisted subordination to imperial jurisdiction.
In the late seventeenth century, in face of French aggression on the Empire’s western borders, the threatened German lands sought to strengthen imperial military functions, organized since the year 1500 in “circles” [Kreise] encompassing multiple principalities. But the Austrian emperors now viewed such developments as curbs on their own military power, which was anchored in their hereditary lands, not in the Empire at large. Though armed enforcement within the Empire of imperial law [Reichsexekution] was militarily allowable, it required congruence between Habsburg and territorial rulers’ interests that, so far as politically weighty states were concerned, never materialized. The Empire could not prevent crippling foreign invasions, notably by the French under Louis XIV (1661-1715) and again in the era of the French Revolution and Napoleon (1789-1815). Nor did it forestall internal war, especially the long and bloody confrontation between Prussia and Austria in the War of the Austrian Succession (1740-1748) and the Seven Years War (1756-1763).