Complex sentence: At the First Synod of Tyre in AD 335, they brought accusations against Athanasius, now bishop of Alexandria, the primary opponent of Arius; after this, Constantine had Athanasius banished since he considered him an impediment to reconciliation.
Split into simpler sentences: At the First Synod of Tyre in AD 335, they brought accusations against Athanasius, now bishop of Alexandria, the primary opponent of Arius. After this, Constantine had Athanasius banished since he considered him an impediment to reconciliation.