Final answer:
The Thirty Years' War started from religious tensions within the Holy Roman Empire, ignited by the Defenestration of Prague and further fueled by political ambitions of European powers. The war ended with the Peace of Westphalia, reorganizing the Holy Roman Empire and confirming French dominance in Europe.
Step-by-step explanation:
The Thirty Years' War began as a conflict fueled by religious tensions between Catholic and Protestant states within the Holy Roman Empire. The spark that ignited this devastating conflict was rooted in the Defenestration of Prague in 1618, an act that demonstrated a vehement refusal to cooperate by Protestant nobles. These nobles responded to the threat of Catholic Habsburg authority by literally throwing two Catholic regents out of a castle window in Prague. This bold demonstration escalated the already-existing religious and political tensions, leading to open warfare.
Catholic and Protestant states, such as German Catholics, Lutherans, and Calvinists, quickly took up arms, and their battles drew in neighboring European countries seeking to advance their own interests. For example, Sweden and the United Provinces of the Netherlands supported the Protestant cause, while France aligned with the Protestants to challenge Habsburg dominance and assert itself as a European power. The resulting war ravaged German lands, with mercenary armies causing widespread destruction. The eventual winners were the German Protestants, and with the signing of the Peace of Westphalia in 1648, the fragmented Holy Roman Empire was reorganized, securing France's position as a dominant European power.