The RC Church, seeing an ally against ‘Bolshevism’ in the Nazi government, quickly came to terms with it in a Concordat of 1933. This was soon dishonoured (e.g. by the suppression of Catholic schools), and in 1937 Pope Pius XII issued a strongly anti-Nazi encyclical Mit brennender Sorge (with burning anxiety). The Concordat was never rescinded, however, and no organized RC resistance emerged, although there were individual heroes.
"Kirchenkampf." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (February 20, 2019). https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/kirchenkampf
"Kirchenkampf." The Concise Oxford Dictionary of World Religions. . Retrieved February 20, 2019 from Encyclopedia.com: https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/kirchenkampf