Did You Know 09: The Cross and the Fish

For three centuries, Christians avoided the cross entirely and hid their faith in a fish symbol instead. Here’s what changed everything.

Did you know? 🤔 The Christian cross wasn’t widely used as a symbol of faith until the 4th century AD. Early Christians often used symbols like the fish (ichthys), anchor, or chi-rho monogram to identify themselves. The cross became prominent after Emperor Constantine allegedly saw a cross in the sky before a battle and subsequently legalized Christianity.

Walk into almost any church today and the cross is everywhere — on the steeple, the altar, around people’s necks. It feels like it must have always been Christianity’s defining symbol. But for roughly the first three hundred years of the faith, Christians largely avoided it, and reached for very different symbols instead.

The reason wasn’t theological hesitation — it was survival. Crucifixion was the Roman Empire’s method of executing criminals, slaves, and rebels, designed to be as humiliating and public as possible. Openly displaying a cross as a badge of faith, during a period when Christianity was frequently outlawed and its followers persecuted, would have been both dangerous and, to Roman eyes, bizarre — proudly wearing the symbol of a slave’s execution. So early believers found quieter, subtler ways to recognize one another. The fish, known by the Greek word ichthys, became one of the most common — the letters of the word formed an acronym for “Jesus Christ, Son of God, Savior,” making it a discreet way to signal shared faith to someone who might be a fellow believer, without announcing it to everyone else. The anchor served a similar purpose, its cross-like shape hidden in plain sight as an ordinary maritime symbol, while doubling as an image of steady hope in troubled times.

Everything changed with a battle. In 312 AD, the Roman general Constantine faced his rival Maxentius at the Milvian Bridge, in a fight for control of the empire’s western half. According to the ancient historian Eusebius, Constantine reported seeing a cross of light in the sky before the battle, accompanied by the words “in this sign, conquer.” He ordered his soldiers to paint the Chi-Rho — the first two Greek letters of “Christ” — on their shields, and went on to win a decisive victory. Whatever actually happened that day, Constantine credited it to the Christian God, and the following year issued the Edict of Milan, legalizing Christianity across the empire and ending the persecution that had driven believers toward quiet symbols in the first place.

With persecution lifted, there was no longer any need to hide, and the symbols of the faith shifted accordingly. The cross, once too dangerous and too shameful to display, was gradually reclaimed as the central image of the very faith it had once threatened — a mark not of humiliation now, but of victory. It’s a striking reversal to sit with: the instrument Rome used to crush Christianity became, once the empire itself turned Christian, the symbol Christianity chose to wear.