One church council in 325 AD settled a debate that had split Christianity for years

In 325 AD, Roman Emperor Constantine I summoned bishops from across the empire to the city of Nicaea to resolve the Arian controversy — a fierce dispute over whether Jesus was of the same divine substance as God the Father. The resulting Nicene Creed became a foundational statement of Christian doctrine still recited in churches today.

— Eusebius of Caesarea, Life of Constantine — 4th-century contemporary account