Thirty Years’ War: what are the causes?

In 1618, the Thirty Years’ War began as an internal religious war in the Germanic Empire but the European powers intervene quickly through the game of alliances and transform the Empire into a European battlefield. The religious factor will take a back seat, since political alliances will be made and broken without taking into account the different faiths of the belligerents.

The origins of the Thirty Years’ War to be found in the Peace of Augsburg of 1555

The Peace of Augsburg adopted on September 25, 1555 marks the beginning of a new era for Germany: it closes the period of Reform and recognizes the coexistence of two denominations: the Catholic Church and the Lutherans; the Calvinists will not be recognized until 1648. Religious freedom is granted to the free princes, states and cities of the Empire; no state of the Empire can attack another under a religious pretext, and a prince cannot be forced to change his religion. The subjects of the States of the Empire must follow the choice of their prince; this is the meaning of the formula invented at the end of the XVI^e century: ” cujus regio, ejus religio (To such and such a sovereign, such a religion).

The provisional compromise instituted by the Peace of Augsburg made it possible to neutralize the religious problem and assured Germany its longest period of peace from 1555 to 1618. With the Peace of Augsburg, the Holy Empire changed its face: to a structure policy based on religious unity, followed by a mosaic of Catholic and Lutheran States. The partition denominational is adapted to the fragmented political structure of the Empire but it weakens it for the benefit of the States which constitute it, since the latter are now in charge of religious questions. The imperial idea (that of an Empire formed of States subject to the superior authority of the emperor) remained very much alive until the 1600s, but the religious divide gradually widened in Germany and led to the beginning of the 17th century.^e century, to the opposition of two blocks ready to clash.

War in the Germanic Empire

In the kingdom of Bohemia at the beginning of the 17th century^e century, the religious situation remains very uncertain because the Peace of Augsburg does not apply to this territory. In 1609, the Germanic emperor Rudolph recognized the freedom of worship of the Protestants of Bohemia. In 1617, Emperor Ferdinand II (who is King of Bohemia) undertakes the large-scale “Catholicization” of Bohemia and provokes the rebellion of the Protestant nobles against the Habsburg monarchy; it is the episode of the “defenestration of Prague” in May 1618.

In August 1619, Bohemia became a confederation of provinces ruled by an elected monarch: King Ferdinand was deposed and the Elector Palatine Frederick (German Calvinist prince) was proclaimed sovereign of Bohemia. Frédéric takes the head of the Protestant Union created by his father to safeguard Protestant interests within the Germanic Empire. The new Bohemian government hopes to have the support of England, the United Provinces and Denmark. The Germanic Emperor Ferdinand II obtains the financial and ideological support of the Crown of Spain, the Pope and the German Catholic Holy League. The battle of the White Mountain (near Prague), November 8, 1620, results in the crushing victory of the Holy League; it is considered to be one of the first and most important battles of the Thirty Years’ War.

The imperial army seizes Bohemia and members of the government are arrested and sentenced to death. The failure of this sling of the princes turns out to be catastrophic for the kingdom of Bohemia: the local nobility is decimated and the new sovereign accentuates the centralization of power. In 1620, the condemnation of Frederick, prince elector of the Palatinate, his banishment from the Germanic Empire and the attribution to the Duke of Bavaria of his office as an elector, led to the entry into the war of the Protestant princes on the side of Frederick: it was the real trigger for the Thirty Years’ War.

The attitude of foreign powers

The Rhine regions were the seat of several battles during the years 1621-1622 and Catholic forces controlled southern and western Germany. The fighting is accompanied by destruction and very significant exactions by the armies in the field. In 1625, Christian IV of Denmark decides to intervene in the conflict: Lutheran monarch vassal of the Germanic emperor, he wants to defend Lutheranism and expand his possessions in northern Germany. The requested France is limited to granting financial assistance to the Danish sovereign. In 1626, the Danes and their German Protestant allies were defeated by the imperial army and its general-in-chief Wallenstein. To save his kingdom, Christian IV was forced to sign the Peace of Lübeck in May 1629: Denmark undertook to no longer intervene in the affairs of the Empire; it is the end of Danish political influence in Europe. Rid of the Danish danger, the Germanic emperor sent his troops to northern Italy, to support the Spanish army which was fighting the French troops sent by Richelieu.

King of France Louis XIII becomes aware of the political imbalance which is established for the benefit of the Habsburgs: he fears a coalition between the king of Spain and the Germanic emperor, which would cause an encirclement of the kingdom of France. French diplomacy is concentrating its efforts on Sweden, the rising power of the Baltic which has just defeated Poland. In January 1631, Gustav Adolf II of Sweden undertakes to maintain an army of 30,000 infantry and 6,000 cavalry in Germany, with financial aid from France of 400,000 ecus per year. The King of Sweden (Protestant) promises to respect Catholic worship and not to wage war on the allies of France.

The reestablishment of peace in Germany was made possible by the signing of the Peace of Prague in May 1635, but France and Sweden opposed the agreement reached by the Germanic Emperor Ferdinand II. We are witnessing a surprising alliance of the Catholic King of France with the Protestant Crown of Sweden. Richelieu decides that the time has come to declare war on Spain. The French armies, 120,000 strong, will intervene in four sectors:

• Spanish Netherlands (caught between France and United Provinces);
• Duchy of Lorraine, Alsace and Franche Comté;
• Northern Italy (Piedmont and Valtellina);
• Pyrenees.

The last great battle is that of Lens, August 20, 1648: Condé at the head of the French army, defeats the Spaniards; Emperor Ferdinand III accepts the peace formalities, negotiations of which have actually lasted for five years. The treaties of Westphalia concluded the Thirty Years’ War on October 24, 1648. They were signed in two separate places for reasons of religious incompatibility:

• in Osnabrück between the Holy Empire, Sweden and the Protestant powers;
• in Münster between the Empire, France and the Catholic powers.

The war between France and Spain is not included in the provisions of the treaties. It is the Treaty of the Pyrenees, signed on November 7, 1659, which formalizes peace between the crowns of Spain and France.

Assessment of the Thirty Years’ War

The Thirty Years’ War ravaged all the regions crossed by the European armies. Some provinces are depopulating in a dramatic way: Saxony, Alsace, Franche-Comté, Lorraine have lost half of their population, two thirds for the Palatinate. North Germany is particularly depopulated: in Pomerania, the population decreases by 65% ​​between 1618 and 1648. France is the “big winner” of this Thirty Years’ War: its European hegemony will assert itself under Louis XIV. It benefits from several very important territorial gains including Alsace.