Sun Simeng, The Official Ideology of External Wars in the Byzantine Empire

　　It has been a controversial issue for a long time in the international academia focusing on the nature of external wars launched by the Byzantine Empire or wars in which it was involved. The major divergence was related to the different views on whether the idea of ‘holy war’ ever existed in the history of the Byzantine Empire. In contrast to the holy war ideas propagandised in the medieval Arab Empire or the Western Crusades, the central claim of the Byzantine concept of external wars reflected in its historical materials remained secular and political to a certain extent. For example, it regarded the defence and recovery of the territory of the ancient Roman Empire as the mere reason to wage an external war, believed that it was the Roman emperors, not the ecclesiastical hierarchies, who had the authority to wage war, prohibited clergymen from taking arms to fight, and in most cases described enemies in terms of their ethnic traits instead of their religious belief. Accordingly, numerous theological and historical works from the Byzantine perspectives recorded, analysed and refuted the religious propaganda and clergymen's participation during the Arab conquests and Crusades. In the elite writings and imperial military practices during the Byzantine period, the influence of Christianity was manifested in the belief that the Christian faith could limit acts of violence and merely play a limited supporting role in wars against foreigners. In their opinions, the Byzantine army could receive the Heavenly aid only if the war began with a righteous cause and was carried out with devout religious rites.