The Schmalkaldic League, an alliance of Lutheran princes and cities that pledged to protect each other from any religiously motivated attack lasted for sixteen years. The Reformation had further divided Europe already fragmented by cultural, economic and political differences. In the Holy Roman Empire, which covered much of central Europe, the newly Lutheran princes clashed with their Emperor: he was the secular head of the Catholic Church and they were part of a heresy. They banded together to survive.
The Empire Divides
In the mid-1500s the Holy Roman Empire was a piecemeal grouping of over 300 territories, which varied from large dukedoms to single cities; although largely independent, they all owed some form of loyalty to the Emperor. After Luther ignited a massive religious debate in 1517, via the publication of his 95 Theses, many German territories adopted his ideas and converted away from the existing Catholic Church. However, the Empire was an intrinsically Catholic institution, and the Emperor was the secular head of a Catholic Church that now regarded Luther's ideas as heresy. In 1521 Emperor Charles V pledged to remove the Lutherans (this new branch of religion was not yet called Protestantism) from his kingdom, with force if necessary.
