Thirty Years' War started out as a war of religion, and then almost all European entities got involved in it. It was concluded by the Peace of Westphalia in 1648, which led to a great deal of changes in European politics, but especially to the reorganization of the Holy Roman Empire.
Even though the significance of the Peace of Westphalia as a watershed moment in the European history is seldom debated, I am given to understand1 that there are two opposing viewpoints about a certain aspect about it. According to one viewpoint, the Thirty Years' War and the Peace of Westphalia mark as the events after which religious politics played a little part in the diplomatic relations amongst European powers, i.e. after 1648, diplomatic relations amongst European entities were dominated by secular issues. On the other hand, some historians argue that the Peace of Westphalia did not mark such a dramatic transition from religious to secular politics.
As far as I know, the first viewpoint seems reasonable -- most of the major wars that happened after the Thirty Years' War had purely secular origins. What are some of the arguments put forward by the opposing side to justify that religion still played a significant part in the international diplomatic decisions? (Note that here I am ignoring the part religion played in the internal politics -- for example any civil war that might have its origin in religion.)