This is an excellent summary of the beginning of the end of two great empires. The Arabs would destroy the Persian Sassanids completely. The Byzantine with the loss of their bread basket of Egypt and Africa would be permanently weakened. The Crusades of later centuries did not help the Byzantines. The Fourth Crusade where the Crusaders sacked Constantinople left the empire even weaker. The Fourth Crusade is why many of the treasures of Constantinople were brought to Venice.