The Thirty Years' War is the first military conflict that has swept the whole of Europe. Two large groups took part in it: the Habsburg bloc (Austro-Germanic and Spanish Habsburgs, the Catholic princedoms of Germany, Poland) and the anti-Habsburg coalition (Denmark, Sweden, France, Protestant principalities of Germany, England, Holland, Russia). The deployment of this conflict was facilitated by both religious and political reasons.
"War of faith" is the second name of a large-scale military conflict that lasted from 1618 to 1648. Indeed, the Thirty Years' War was the most terrible period of confrontation between Catholics and Protestants in the 17th century. Many people took up arms to establish the rule of the "right faith". The religious character of the war is also evidenced by the names of the opposing alliances. In particular, Protestants created the Evangelical Union (1608), and the Catholics - the Catholic League (1609).
All of the above resulted in the uprising of Prague Protestants on May 23, 1618. Then there was the "Second Prague Defenestration": the rebelling Protestants threw out of the windows of one of the fortresses of Prague Habsburg officials. The latter survived only because they fell into the dung. Later, the Catholic Church explained their salvation by the help of angels. After the events described, the Catholic army moved towards the insurgents. And the Thirty Years' War began.
But the reasons for the Thirty Years' War are connected not only with religion. The political nature of the conflict was clearly manifested in subsequent periods of the war (Swedish, Danish and French-Swedish). It was based on the struggle against the hegemony of the Habsburgs. So, Denmark and Sweden, who defended the interests of Protestants, wanted to gain political leadership in Central Europe. In addition, these countries were fed to get rid of competitors on the northern sea routes.
Thirty years of war contributed to the fragmentation of the Habsburg empire, so even Catholic France took the side of the Protestants. The latter was afraid of excessive strengthening of the empire, and also had territorial claims in the Southern Netherlands, Alsace, Lorraine and Northern Italy. England fought the Habsburgs at sea. The thirty-year war, the causes of which were hidden in religion, quickly turned into one of the most ambitious European political conflicts.