The major causes of the Thirty Years' War in Europe included religious conflict, political power struggles, and territorial disputes. The war began in 1618 primarily as a confrontation between Protestant and Catholic states within the Holy Roman Empire, spurred by the Reformation's religious divisions. Additionally, dynastic ambitions and the quest for power, especially from France, Sweden, and Austria, further complicated the situation. The conflict escalated into a broader European war involving various kingdoms and empires, and it ultimately led to significant changes in the political and religious landscape of Europe, particularly through the Peace of Westphalia in 1648.