The Eastern Church continued to decline with the Eastern Roman (Byzantine) Empire, undercutting Constantinople's claim to equality with Rome. Twice an Eastern Emperor tried to force the Eastern Church to reunify with the West. First in the Second Council of Lyon (1272–1274) and secondly in the Council of Florence (1431–1449). Papal claims of superiority were a sticking point in reunification, which failed in any event. In the 15th century, the Ottoman Empire captured Constantinople and ended the Byzantine Empire.