Answer:
With the invasions of the 8th century the Byzantine State was paralyzed and would never regain its former power. In 1369, Emperor John V sought financial help from the West to face the growing threat of the Turks. The arrival of the paleologist of Emperor Michael VIII marked the beginning of a prolonged decline for the Eastern Roman Empire.
Under the mandate of John's successors, the Empire was able to get some relief from the Ottoman oppression thanks in part to the fact that the Persian and Ottoman peoples were still too divided to attack. Finally, after the appointment of Murad II as a sultan in 1421, the truce had come to an end. Murad revoked all the privileges granted to Byzantium and began to conquer all his lands.