The first persecution by an emperor occurred under Nero, and was confined to the city of Rome. Tacitus reports that after the Great Fire of Rome in AD 64, some among the population held Nero responsible and that the emperor attempted to deflect blame onto the Christians. After Nero, a major persecution occurred under the emperor Domitian and a persecution in 177 took place at Lugdunum, the Gallo-Roman religious capital. A surviving letter from Pliny the Younger, governor of Bithynia, to the emperor Trajan describes his persecution and executions of Christians. The Decian persecution of 246–251 was a serious threat to the Church, but ultimately strengthened Christian defiance. Diocletian undertook what was to be the most severe persecution of Christians, lasting from 303 to 311.