it happened for roughly 400 years when the Romans persecuted the Christians..
The popular idea that Romans were constantly throwing Christians to lions in a non-stop orgy of persecution for hundreds of years isn't really true.
The first persecution was by Nero in AD67, when, according to Tacitus, he blamed Christians for the great fire of Rome and ordered those in the City of Rome put to death. tbf, Nero persecuted everybody, Pagan and Christian.
For the next 182 years there wasn't really any organised persecution of Christians at all. There were sporadic local persecutions that seem to be more about local governors or villagers dealing with awkward followers of the apocalyptic cult spreading amongst slaves and the rural poor that kept making a nuisance of themselves trying to save the souls of those around them. These stepped up during during the reign of Marcus Aurelius (reigned 161–180), but how organised or widespread they were is subject to debate.
The first big persecution came in 249, when Emperor Decius declared that all Romans must burn some incense at their local temple as a sign of loyalty to him, on pain of death. It wasn't specifically targeted at Christians, but the devout refused to make a sacrifice to a false God, preferring to go to heaven a martyr than suffer in the afterlife for worshipping false idols. That led to lots of Christians being put to death. There's records of local governors begging Christians to make the sacrifice to save their lives, but the devout chose martyrdom instead.
His successor Gallus (reigned 251 - 253) is said to have persecuted Chistians, but the only recorded examples are his exiling two popes
Then there seems to have been little persecution for the next 45 years until the reign of Emporor Diocletian (284 -305). During his reign he became focussed on suppressing non-Roman religions and in 303 he issued a series of edicts rescinding Christians' legal rights and demanding that they comply with traditional religious practices. For 3 years there was a purge of Christians in the Roman empire until his son Constantius Chlorus restored Christian's legal rights in 306 during his brief reign.
He was succeeded in 306 by Emperor Constantine, who famously converted to Christianity. From then on Rome increasingly suppressed followers of the old gods. Constantius II (reigned 337 - 361) closed all pagan temples and made pagan sacrifices punishable by death. Theodosius I (379 - 395) abolished all pagan cults and ceremonies, including the Olympic Games.