The main cause of the Great Schism in the Catholic Church was the culmination of political, theological, and cultural differences between the Eastern (Orthodox) and Western (Catholic) branches of Christianity. Key issues included disagreements over papal authority, the use of unleavened bread in the Eucharist, and the Filioque clause in the Nicene Creed. Tensions came to a head in 1054 when mutual excommunications were issued, formalizing the divide. Political factors, such as the rise of the Byzantine Empire and the westward expansion of Latin Christendom, also played significant roles in the schism, fundamentally altering the landscape of Christianity for centuries to come.