When the Roman government began to persecute Christians under Nero,

Many Christians were died or killed when the Roman government began to persecute Christians under Nero, because the Christianity was declared illegal at that time.

Explanation:

The Roman Emperor Nero accused the Christians for starting the fire that burnt the whole Roman Empire. It was believed that the Christian religion was the counter religion to the traditional Roman religion. In Rome the great fire was caused because of the persecution of the Christians and because of influence of Christianity in traditional Roman religion. In 64 AD the collosal fire destroyed much of the the Roman cities. The Christians were persecuted in the next hundred years by the upcoming emperors.