The differences between the earlier emperors and Decius
, Valerian and Diocletian were that no real edicts were made requiring Christians to sacrifice to pagan gods. Even though laws were passed by earlier emperors trying to prevent the power and growth of the Christian Church the persecution could have been avoided by simply moving to another city or province in the Roman Empire. As we see with Trajan's reply to Pliny in regards on what to do with Christians we find that the emperor was not all that concerned with hunting the Christians down and actually advises not to do so, this is different to Diocletian especially where he actually goes out of his way to remove all Christians from the army and targets a specific Christian sect.