3 You are aware, venerable brothers, of how the mutual understanding which reigned so long between the Apostolic See and the kingdom of Prussia was thrown into sudden disorder by these laws, placing Catholic citizens in such great danger and distress. But this disaster which caused so much sorrow to Our predecessor Pius IX and to Us has offered God an opportunity. Thus the virtue of the pastors and faithful of Germany and their adherence to the faith of their fathers shine forth all the more. This virtue, this loyalty is so much more worthy of praise when strenuous efforts to protect the interests of the Church have preserved the respect and submission due to the Prince and the proper love of country. Catholics have thus shown their adversaries that they acted not for political considerations but solely from religious duty, which commands the preservation of the sacred and inviolate work of God. Thus, God, the supreme author and rewarder of all merit, has bestowed the fullest treasures of His goodness and grace on you, venerable brothers, and on all the people of your dioceses. His helping hand was ever present, while the new laws diminished daily the number of priests among the Prussian faithful and left many parish churches without pastors. Those treacherous men who call themselves "old Catholics" spread new and perverse teachings and strove to attract to themselves unfortunate disciples deceived by fraud. Nevertheless, We have seen with joy Our dear sons, the Catholics of Germany, hold firmly and fully to the faith of their fathers. The snares of the masters of deceit have never prevailed against them, for with Christian courage they have triumphed over danger. They attached themselves to the Church with a love so much the greater as they saw it the object of harsher trials.
Source: Iampridem (Vatican.va)