Diocletian had ruled for eighteen years without moving against the Christians, and the persecution that began in 303 was late, systematic and, in the event, futile. The first edict ordered churches demolished, scriptures surrendered and burned, Christians of rank stripped of privileges and Christian slaves barred from freedom. Further edicts imprisoned the clergy, then required them to sacrifice, then extended the requirement to everyone.
Enforcement varied enormously by region, and the variation matters. In the East, and especially in Egypt and Palestine, it was severe and prolonged. In the western provinces under Constantius it was light, largely limited to the demolition of buildings. The persecution therefore fell hardest exactly where the Christian population was largest, and produced the martyr literature that shaped Christian memory of the whole imperial period.
It ended, remarkably, with an admission of failure. In 311 Galerius, dying of a painful illness, issued an edict acknowledging that the policy had not returned the Christians to the old religion and had left many worshipping nothing at all, and permitting them to exist again and to rebuild their meeting places, asking their prayers in return. That document, two years before the arrangement usually called the Edict of Milan, is the legal end of persecution as imperial policy.