The persecutions culminated with Diocletian and Galerius at the end of the third and beginning of the 4th century. Their anti-Christian actions, considered the largest, were to be the last major Roman pagan action. The Edict of Serdica, also called Edict of Toleration by Galerius, was issued in 311 in Serdica (today Sofia, Bulgaria) by the Roman emperor Galerius, officially ending the Diocletianic persecution of Christianity in the East. Constantine the Great soon came into power and in 313 completely legalized Christianity. It was not until Theodosius I in the latter 4th century, however, that Christianity would become the official religion of the Roman Empire.