Answer
Cyril of Alexandria, the prominent churchman of the time, clashed with Nestorius, the Archbishop of Constantinople, due to theological disagreements. Nestorius propounded a doctrine that distinguished the divine and human natures of Christ, while Cyril upheld the belief in their inseparability. This conflict, known as the Nestorian Controversy, led to Nestorius' condemnation and exile, contributing to the larger Christological debates that shaped early Christian theology.