Complex sentence: Cardinal Bertram developed an "ineffectual protest system" and only gradually did Catholic resistance re-emerge, in the form of the efforts of individual clerics like Cardinal Preysing and Bishop Galen.
Split into simpler sentences: Cardinal Bertram developed an "ineffectual protest system". Only gradually did Catholic resistance re-emerge, in the form of the efforts of individual clerics like Cardinal Preysing and Bishop Galen.