Before Constantine became the emperor of Rome, the Christians suffered many persecutions. Warrants went out, advising anyone who suspected a Christian to report them to the authorities. When caught, the officials gave the Christians a choice: curse God and Jesus and worship the Roman gods, or die. Torture methods were enacted upon those who refused until they complied or until they died. Constantine ended all this with the Edict of Milan in A.D. 313.
Pliny, a governor, asked Trajan, the emperor at the time, for counsel in dealing with the Christians. The answer was basically that if the citizens and neighbors of Christians denounced them, they would be captured and executed. To him simply being a “Christian” was enough to impose negative sanctions on him. Those “Christians” who complied with the Roman officials’ order to curse God and Jesus were set free. Some of the false Christians even insisted that they had converted to the Roman pagan religion before they were on trial. A few of them claimed they had reverted back years before to Rome’s pagan religion. Diocletian, the emperor from 303-305 A.D., forced citizens to come out and worship Roman gods publicly. In this way he was able to weed out Christians and execute them.
Constantine made the Edict of Milan which freed the Christians from oppression for their faith. He had sympathy for them partly because he believed that God had helped him to power. This merciful act gave Christians the freedom to worship as they pleased. Many people were then unafraid to “convert”.