The 30 Years War
Swedish, French, and Post-War (1618-1648)
Sweden Campaign
There were several attempts by Protestants to overthrow Roman Catholic rule. Much of the fighting took place in Germany, but none of it was successful. Sweden had influence there and they wanted to maintain that power. The Imperialists, or the HRE Armies, were a threat, so in 1630, a military led by Swedish King Gustavus Adolphus invaded Germany. Funded by French coin, the Swedes turned the tables, ultimately saving the Protestant cause. This revival lasted until 1634 when a Spanish army forced the Protestants to leave Germany.
French Campaign
After the Spanish victory in 1634, the French were afraid of encirclement, which prompted them to declare war on Spain in 1635 and the HRE in 1636. This time, France needed money, so Sweden funded their war efforts. France fought for about ten years which eventually prompted the exhausted Hapsburgs to think about making a treaty. The Thirty Years War was anti-climatic because no side definitively won, but there were consequences.
After the War
The signing of the Peace of Westphalia had several effects. First of all, France and Sweden were strengthened because the treaty gave them several territories. Also, the treaty took away much of the influence of the Holy Roman Empire because some their land was distributed to France and Sweden. The foundation for a unified Germany was laid when Brandenburg gained that land. Switzerland became an independent confederation. The Netherlands obtained freedom. Calvinism was an acceptable religion after the war ended. Perhaps most importantly, religion would never again be the root of a war.