The main reason for the Great Schism between the Catholic and Orthodox Churches, which formalized in 1054, was rooted in theological, political, and cultural differences. Key issues included disputes over papal authority, with the Catholic Church asserting the supremacy of the Pope, while the Orthodox Church favored a conciliar model of leadership. Additionally, differing practices such as the use of unleavened bread during Communion and the filioque controversy (the phrase "and the Son" in the Nicene Creed) further deepened the divide. Political tensions, shaped by the rise of Byzantine power and the growing influence of Rome, exacerbated these differences, leading to a significant and lasting division in Christianity.