The Protestant Reformation ignited by Martin Luther opened the door for many others to express their dissatisfaction with the Roman Catholic Church in Sixteenth Century Germany. The expression was not simply a verbal argument; the Protestant princes mustered armies among their followers, and responded to Catholic edicts with violence. The fact that Church lands were confiscated by force was distressing to the Catholic leaders. Charles V, King of Germany at the time of the Protestant Reformation, attempted to settle the religious quarel between the Protestants and Catholics by discussion and arbitration. When that effort failed, he resorted to force in the attempt to crush the Protestant armies. The Lutheran Princes joined in an alliance with the French king, Henry II, who was promised the border cities of Metz, Toul and Verdun if he supplied French aid to their cause. Charles realized what a war with France would entail, and offered a compromise.
The Peace of Augsburg in 1555 promised to the territorial princes the right to decide whether Catholicism or Lutheranism would be admitted within their respective realms. If the common man within a particular territory disagreed with the faith that the prince of that territory chose, he would be permitted to emigrate with his family to another territory. A second provision was that only Lutheranism, of the various Protestant sects, would be permitted in opposition to Catholicism. Lands which were in Lutheran possession at the time of the Treaty of Passau (1552) would remain under such ownership, but thereafter, if a Catholic bishop or other ecclesiastical leader were to convert to Lutheranism, he would have to forfeit his lands and property.
The Peace of Augsburg was flawed and, in part, served as a cause of the Thirty Years War that would erupt in 1618. It was difficult to enforce the provisions. On the one hand, the provision calling for the forfeiture of property was openly violated and flaunted. Catholic princes of territories throughout Germany professed a conversion to Lutheranism, but converted the Church properties within their realms into private holdings. On the other hand, the Peace of Augsburg recognized only Lutheranism as a valid Protestant sect. The Calvinists, Anabaptists and others resented being excluded from the Peace of Augsburg's provisions. It was because of the latter problem that the Protestant Union was formed. The Union was led by a Calvinist prince by the name of Frederick, the Elector Palatine of the Rhine.
The ambitions of Emperor Matthias, the Habsburg king of Austria posed a threat to both, the Protestants and the Catholics. But the Catholic princes formed a League, led by Maximilian of Bavaria, to counter the Protestant Union. The Catholic League decided to support the Habsburg king, who professed his devout Catholic faith. Matthias was childless, and his choice for successor was Ferdinand of Styria, who was likewise loyal to Catholicism. The choice of Ferdinand was accepted in Austria and most of the other regions that fell under the direct control of the Habsburg king. But in Bohemia, the predominantly Calvinist noblemen staged a protest against another Catholic king over their territories. They declared the dethronement of the Habsburg dynasty and then proclaimed the election of Frederick, the Elector Palatine of the Rhine as their new king.
King Ferdinand responded to the Bohemian challenge by enlisting the aid of a Spanish army to invade the Palatinate region of Germany, and with Maximilian of Bavaria to invade Bohemia with his own army. The Catholic forces were victorious in this initial foray. From that point the war escalated into an international conflict. The Spanish king, Philip IV saw his success in destroying the Palatinate as simply a stepping stone to retaking possession of Holland. The invasion of Holland by the Spanish brought England and France into the conflict on the behalf of Holland. The war even spread across the Atlantic Ocean to Brazil in South America. King Christian IV of Denmark and Norway, the Duke of Holstein, and as such a member of the Holy Roman Empire, invaded Germany in an effort to overthrow the Habsburg dynasty. The predominantly Lutheran nation of Sweden joined in the war as an ally of the Protestant Union, it is said, because she feared in Germany fell to the Papists, Sweden would be next.
The Thirty Years War was finally brought to a conclusion with the Treaty of Westphalia, which was signed on 24 October, 1648. The terms of the treaty included the extension of the same rights to the Calvinists as those that had been extended to the Lutherans in the Peace of Augsburg. The Upper Palatinate was ceded to Bavaria. The Lower Palatinate was restored to the eldest son of Frederick, the Elector of the Palatinate of the Rhine. Western Pomerania, including Bremen and Verden, was ceded to Sweden. Brandenburg received the bishoprics of Camin, Halberstadt, Minden and a large portion of Magdeburg. France obtained the Alsace, with the exception of Strasburg; she also retained possessionof Metz, Toul and Verdun. The United Provinces of the Netherlands (i.e. Holland) and Switzerland received their independence from the Empire.
The results of the Thirty Years War, in spite of the devastation wrought on Germany included a certain amount of religious freedom and the emergence of "modern" statehood in Europe. In the end, not all of the Protestant sects were granted equal liberty; only Lutheranism and Calvinism were afforded legal status alongside Catholicism. But since it was the Calvinists who instigated the conflict, they were satisfied with the settlement. Of importance to the Protestant Union was the curtailment of the Habsburg dominance in Germany. The prestige of the Holy Roman Empire was shattered as a result of the war, and as a result, it emerged as simply one of the many "sovereign states" of Europe.