5 We will easily understand how great was the task undertaken by this strong defender of the Catholic faith in the interest of the Church and of society if We consider the situation in Germany at the beginning of the Lutheran revolt. Moral standards had changed and as they continued to worsen, it was easy to fall into error - but this very error hastened the final collapse of morals. The number of those leaving the Catholic faith gradually increased. Soon the poison spread to most of the provinces and infected all classes. Many considered the cause of religion in that realm to be desperate and doubted that any remedy remained to be tried. Indeed it is clear that all would have been lost if God had not intervened with powerful aid.
Source: Militantis Ecclesiae (Vatican.va)