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How did the Council of Nicaea respond to the teachings of Arius?

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Abu El-Abbas mosque in Alexandria, Egypt, featuring ornate domes, arched entrances, intricate stonework, and a large patterned courtyard in the foreground. — Alexandria The mosque of Abū al-ʿAbbās al-Mursī, Alexandria, Egypt.

The First Council of Nicaea, convened in 325 CE, responded to the teachings of the Alexandrian presbyter Arius by formally condemning him as a heretic.123

The council’s primary objective was to resolve the controversy surrounding Arianism, which posited that Christ was a created being rather than equal in divinity to God the Father. When Arius refused to sign a formula of faith affirming that Christ was of the same divine nature as God, the council denounced his views. Following this condemnation, Emperor Constantine I exiled Arius.132

To safeguard orthodox belief, the council issued a creed incorporating the term homoousios ("of one substance"), which explicitly declared the Son to be completely divine and equal to the Father. Despite these measures, the dispute persisted for decades, as Arianism remained influential in the Eastern Roman Empire until it was definitively proscribed at the First Council of Constantinople in 381.134