The fire
In July AD 64, a fire broke out in Rome. It burned for days and destroyed much of the city. Rumours spread that the Emperor Nero had started it himself.
Nero needed someone to blame.
Who Tacitus says he blamed
Tacitus, the great Roman historian, tells what happened next. He was no friend of the Christians. That makes his account all the more valuable:
"Consequently, to get rid of the report, Nero fastened the guilt and inflicted the most exquisite tortures on a class hated for their abominations, called Christians by the populace."
Then he explains who these people were: followers of "Christus," executed under Pontius Pilate in the reign of Tiberius.
An immense multitude
This is the detail that matters most:
"Accordingly, an arrest was first made of all who pleaded guilty; then, upon their information, an immense multitude was convicted."
Jesus was crucified around AD 30, in a small province at the edge of the empire, with a handful of frightened followers.
Barely thirty years later, there were so many Christians in Rome, the capital of the world, that the emperor could blame a city-wide disaster on them, and "an immense multitude" could be rounded up.
Paul had written to them only a few years before: "your faith is spoken of in the whole world" (Romans 1:8).
What was done to them
Tacitus describes it:
"Covered with the skins of beasts, they were torn by dogs and perished, or were nailed to crosses, or were doomed to the flames and burnt, to serve as a nightly illumination, when daylight had expired."
Sewn into animal skins and thrown to dogs. Crucified, like their Lord. Set alight in Nero's gardens to light up the night.
It was during this persecution, the early Church records, that Peter was crucified and Paul was beheaded in Rome (Eusebius, Church History 2.25).
Jesus told them
None of this took his followers by surprise. Jesus had warned them:
"Remember my word that I said to you: The servant is not greater than his lord. If they have persecuted me, they will also persecute you."
John 15:20
Why this is a big deal
This comes from a Roman historian who called Christianity "a most mischievous superstition." He had every reason to play it down.
Instead, he records that within a single generation, the followers of a crucified Jewish teacher had filled the capital of the empire, and that they went to the dogs, the crosses and the flames rather than give him up.
A movement built on a lie doesn't grow like that, under that kind of pressure, that fast.