What role did religion play in the thirty years war?

The Thirty Years' War was an extremely violent conflict which took place in Europe between 1618 and 1648. Religion was instrumental in triggering the war: it began when the Holy Roman Emperor, Ferdinand II of Bohemia, tried the limit the religious freedoms of some of his subjects.

But, as the war progressed, religion became of less and less importance as political and dynastic factors came to the forefront. When France (a Catholic country) entered the war in 1635, for example, it did so as an ally of the Protestant countries of the Netherlands and Sweden, in the fight against Catholic Spain. At this time, the Spanish Habsburgs ruled much of Europe and so the war became a struggle for dominance between this ruling dynasty and the French. The war thus became a competition over who would be the dominant force in Europe.