The Ratification of the Treaty of Münster, 15 May 1648, by Gerard ter Borch.
In short, the main causes of the Thirty Years' War (1618-1648) were the religious conflicts between Catholics, Lutherans and Calvinists; authoritarianism of the house of Habsburg in the exercise of the Holy Roman Empire; Habsburg commercial hegemony in the Baltic; and the Franco-Spanish conflict.
Princes and bishops chose one German king to be crowned by the Pope as emperor of Christendom, since 962 when Pope John XII awarded the title Otto "The big". Thus was born, then, the First Reich (First German Empire). I should add that it was Fredrich, known as "Barbarossa" (1123-1190) who coined the term "Holy Roman Empire" when trying to submit multiple times to the Holy See: the disputes between the altar and the throne.
German Westphalia is a region that includes most of the Ruhr River basin, where agreements were reached to put an end to the Thirty Years' War. The two cities chosen to conduct peace negotiations were Münster, chosen by Catholics; and Osnabruck, by Protestants.
Westphalia agreements were carried out in two conferences:
• The Munster agreement, where Catholics States met. The Spanish monarchy came to an agreement with the United Provinces (Netherlands) to recognize the independence led by the Netherlands and which ended the political-territorial war between these Provinces and Spain. Additionally, a second agreement signed in Münster brought about peace between France and the Holy Roman Empire. That is, an agreement between Catholics States.
• The Osnabruck agreement, where Protestant Swedes negotiated with the Holy Roman Empire. In other words, it was an agreement between Catholics and Protestants.
The agreements signed in Münster and Osnabrück went down in history with the generic name of the Peace of Westphalia. However, some outstanding issues were resolved. Today is the anniversary of the signing in 1648.