Complex sentence: The Edict of Thessalonica, also known as "Cunctos populos", was an edict issued in 380 AD, that ordered all subjects of the Roman Empire to profess the faith of the bishops of Rome and Alexandria.
Split into simpler sentences: The Edict of Thessalonica, also known as "Cunctos populos", was issued in 380 AD. It ordered all subjects of the Roman Empire to profess the faith of the bishops of Rome and Alexandria.