Strong tensions between Catholics and Protestants
The spread of Protestantism in its Lutheran version in German states in the sixteenth century led to clashes between Lutheran princes and princes remained Catholic under the leadership of Emperor Charles V. In 1555, the Peace of Augsburg suspended hostilities by requiring each state religion of its prince. Lutheranism continued to grow until 1570 while Calvinism new confession not recognized by the Peace of Augsburg, was spreading. The Frederick III, Elector of the Palatinate made it the religion of their states.
Catholic reconquest made tensions rise: from 1552 the Jesuits had founded in Rome the German College for lost ground in Germany. The Tridentine Reform