Religious war in Europe may be understood in light of the existing order. First of all, the state and the church were vitally connected. This relationship had existed for centuries, had now, whether. Whether Protestant or Catholic, the state exercised its responsibility to protect and promote the religion of its domain.
Second, religious toleration was at first nearly nonexistent. The idea that two or more religions could exist in the same country at the same time was considered neither possible nor proper to the sixteenth-century mind. This explains the conflict between Catholic and Protestants. But it also explains the intolerance among some Protestants, such as when certain Lutheran rulers persecuted Anabaptists.
Finally, the religious wars were fueled by the political ambitions of the kings of Europe, who saw the highly motivated armies under region's banner as tools to advance their political goals. Nowhere is this more evident than in the 1640s when French Catholics fought Spanish Catholics to aid German Lutherans and Dutch Calvinists.
