Today is the 1700th anniversary of the Battle of the Milvian Bridge. On October 28, 312, Constantine defeated his rival emperor, Maxentius, as the two fought for the city of Rome and control over the western half of the Roman Empire. The defeat of Maxentius is a significant step in Constantine’s quest to become master of the entire Roman Empire, but historians have usually emphasized it as the turning point in his relationship with Christianity.

His biographer, Eusebius of Caesarea, Constantine’s biographer, claims that on the night before the battle, Constantine saw two Greek letters in a vision, a Chi and a Rho. These two letters are the first two letters in the Greek spelling of “Christ.” Along with the letters, Constantine received the message, “In this sign you will conquer.” He took this divine message to mean that God was on his side. He put the Chi-Rho on his soldiers’ shields, and when he defeated Maxentius the next day, he gave Christ the credit.

It’s hard to say when or if Constantine became an orthodox Christian, but after the Milvian Bridge, Constantine begins to favor Christianity. The next year, he issued the Edict of Milan, which formally ended persecution of Christians. The previous ten years had been some of the most difficult times for the church because the previous emperor, Diocletian, believed that Christianity destabilized the empire. Constantine didn’t just legalize Christianity; the Edict of Milan also reimbursed the church for confiscation and damages.

Later, when he had reunited the two halves of the empire and ruled over them as the sole emperor, Constantine built a new capital called Constantinople. This new capital would be unique in the Roman Empire because Constantine constructed church buildings within the very heart of the city. In Rome and most other urban centers, churches had to build their structures outside the city. Constantine architecturally proclaimed that Christianity would be an integral part of his new Rome.

Constantine favored Christianity with money and attention and set a trajectory for its continued growth. He did not, however, make Christianity the official religion of the empire. That move would be made a few generations later. During his life, Constantine probably never imagined a worldwide Christianity. He was merely favoring a formerly persecuted sect. But the bishops knew. They knew that Christianity’s mission was for all to hear the good news. And they took advantage of the good times just as they did the bad.