The Diocletian Persecution of Christians in the Roman Empire officially ends in the East, the last area in which they were still being conducted. Constantine had ended the persecutions in the West in 306.
Galerius, who is thought to have gotten Diocletian to start the persecutions in the first place, ends the persecutions himself from his deathbed.
From the letter of Galerius ending the Diocletian Persecutions:
"Among all the other arrangements that we are always making for the benefit and utility of the state, we have heretofore wished to repair all things in accordance with the laws and public discipline of the Romans, and to ensure that even the Christians, who abandoned the practice of their ancestors, should return to good sense.
Indeed, for some reason or other, such self-indulgence assailed and idiocy possessed those Christians, that they did not follow the practices of the ancients, which their own ancestors had, perhaps, instituted, but according to their own will and as it pleased them, they made laws for themselves that they observed, and gathered various peoples in diverse areas.
Then when our order was issued stating that they should return themselves to the practices of the ancients, many were subjected to peril, and many were even killed.
Many more persevered in their way of life, and we saw that they neither offered proper worship and cult to the gods, or to the god of the Christians. Considering the observation of our own mild clemency and eternal custom, by which we are accustomed to grant clemency to all people, we have decided to extend our most speedy indulgence to these people as well, so that Christians may once more establish their own meeting places, so long as they do not act in a disorderly way. ...
Consequently, in accord with our indulgence, they ought to pray to their god for our health and the safety of the state, so that the state may be kept safe on all sides, and they may be able to live safely and securely in their own homes."
So Christians will no longer be tortured and killed because they are Christians, but they are still admonished for not following the religious customs of their ancestors and they are still expected to pray for the emperor as a substitute for offering sacrifices to the pagan gods. Thus even now Christians are expected to use their religion in a way that benefits the stability and order of the government.