They ended the Thirty Years' War (1618–1648) and brought peace to the Holy Roman Empire, closing a calamitous period of European history that killed approximately eight million people.

[2][3] These treaties ended the Thirty Years' War in the Holy Roman Empire, with the Habsburgs (rulers of Austria and Spain) and their Catholic allies on one side, battling the Protestant powers (Sweden and certain Holy Roman principalities) allied with France (though Catholic, strongly anti-Habsburg under King Louis XIV).

However, some historians have argued against this, suggesting that such views emerged during the nineteenth and twentieth century in relation to concerns about sovereignty during that time.

These negotiations were initially blocked by Cardinal Richelieu of France, who insisted on the inclusion of all his allies, whether fully sovereign countries or states within the Holy Roman Empire.

[7][page needed] In Hamburg, Sweden, France, and the Holy Roman Empire negotiated a preliminary peace in December 1641.

[citation needed] The main peace negotiations took place in Westphalia, in the neighbouring cities of Münster and Osnabrück.

[citation needed] Sweden preferred to negotiate with the Holy Roman Empire in Osnabrück, which was controlled by Protestant forces.

[20] The independence of the Dutch Republic, which practiced religious toleration, also provided a safe haven for European Jews.

[20] The Holy See was very displeased at the settlement, with Pope Innocent X calling it "null, void, invalid, iniquitous, unjust, damnable, reprobate, inane, empty of meaning and effect for all time" in the papal brief Zelo Domus Dei.

[24][25] The Peace of Westphalia also set up new rules for the Reichskammergericht (Imperial Chamber Court), and stipulated that half its judges must be Protestant.

[20] The main tenets of the Peace of Westphalia were: The treaties did not entirely end conflicts arising out of the Thirty Years' War.

[36][page needed] Most modern historians have challenged the association of this system with the Peace of Westphalia, calling it the "Westphalian myth".

While the treaties do not contain the basis for the modern laws of nations themselves, they do symbolize the end of a long period of religious conflict in Europe.