One ground for these persecutions was that it was a crime against the state to refuse to worship the gods of the Romans under whom the Empire had flourished.
It was also the custom to burn incense in front of the Emperor's statue, as an act of adoration.

The Christians not only refused homage to the Roman gods, but denounced the burning of incense as sacrilegious.
AURELIUS gave his sanction to the most general persecution this sect had yet suffered.

The last combined effort to suppress them was under DIOCLETIAN, in 284, but it ended with the EDICT OF MILAN in 312, which famous decree gave the imperial license to the religion of Christ..