Final answer:
The long-term causes of the Thirty Years' War were religious tensions between Catholic and Protestant states, as well as power struggles between European nations.
Step-by-step explanation:
A long-term cause of the Thirty Years' War was the ongoing religious tensions between Catholic and Protestant states in the Holy Roman Empire. These tensions had been brewing since the Protestant Reformation in the 16th century, and they escalated into armed conflict in the 17th century. The war was fueled by competing religious and political ambitions, with Catholic and Protestant powers vying for control and influence in Europe.
Another long-term cause of the war was the power struggles between European nations. This included rivalries between major powers like France, England, and Spain, as well as regional conflicts within the Holy Roman Empire itself.