Complex sentence: As Vatican Secretary of State, he had advocated for the controversial Concordat of 1933, hoping it would build trust and respect with the regime, and later assisted with the drafting of the "Mit brennender Sorge" anti-Nazi encyclical.
Split into simpler sentences: As Vatican Secretary of State, he had advocated for the controversial Concordat of 1933, hoping it would build trust and respect with the regime. He later assisted with the drafting of the "Mit brennender Sorge" anti-Nazi encyclical.