The Council of Nicaea in 325 condemned the position and produced a creed confessing the Son as begotten and not made, and as homoousios, of one substance with the Father. The word was not an obvious choice. It is not scriptural, and a form of it had been rejected in an earlier condemnation, which is why many bishops who had no sympathy at all with Arius were uneasy about it.
That unease is why the council did not settle anything for sixty years. The decades that followed produced a spectrum rather than two camps: a party preferring homoiousios, of like substance, which wanted to affirm the Son divinity while avoiding a word suggesting the Father and Son are one thing; a homoian party content to say simply that the Son is like the Father, which had imperial backing for a period; and a group holding the Son to be unlike the Father, which was the sharpest form of the original position. Bishops were deposed and restored repeatedly as emperors changed.
The settlement came with the work of Athanasius and then the Cappadocian theologians, who supplied a vocabulary distinguishing one substance from three persons, and with the Council of Constantinople in 381. By then the mission of Ulfilas had carried a non-Nicene creed to the Goths, and the Germanic kingdoms established in the western empire, Visigothic, Ostrogothic, Vandal and Lombard, held it for generations. Historians now generally call that Homoian rather than Arian, since its content is not simply what Arius taught.