Why did foreign powers such as Sweden and France take part in the Thirty Years’ War?

Foreign powers like Sweden and France intervened in the Thirty Years’ War primarily to counter the growing power of the Habsburgs and to secure their own strategic and political interests in Europe.12

Sweden’s Motivations

Sweden’s involvement was driven by a combination of security, economic, and religious concerns:
* Security and Influence: Sweden sought to protect its interests in the Baltic region and ensure that no single power, particularly the Holy Roman Empire, could dominate the area.13
* Protestant Support: As a leading Protestant power, Sweden intervened to support German Protestant states against the Roman Catholic imperial forces.12
* Economic Ambitions: Historians have noted that Sweden aimed to control the Baltic coastline to monopolize trade between Russia and Western Europe, seeking territorial cessions like Pomerania to cover war expenses.42

France’s Motivations

France’s participation was largely defined by "reason of state" rather than religious alignment:
* Anti-Habsburg Policy: France sought to prevent the encirclement of its borders by the Habsburgs of the Empire and Spain.12
* Geopolitical Dominance: Cardinal Richelieu aimed to defeat Habsburg hegemony to establish France as the preeminent power in Europe.52
* Strategic Control: France intervened to block Spanish military corridors, such as the land bridge connecting the Netherlands to Italy, and to forestall Spanish preponderance on the Continent.2