Nour al-din Mahmoud Zangi's political relations with Roman and Byzantine Saljuks, a fluctuation from convergence to divergence

Formation of Raha`s and Antioch`s Cruciate governments in the north of Sham and their military threats against Islamic states in that reign caused political convergence and alliance between Nour al-din Mahmoud Zangi`s government and Roman Seljuks، during Masoud ibn Ghalich Arsalan era. The union had mutual advantages for the two sides. After Raha`s government demolished، Antioch weakened and Nour al-Din`s government established، the union ended. Nour al-din`s power threatened Roman Saljuks. So، the conflict between the two governments caused divergence between them. Then، Nour al-Din got closer to Byzantium because of common interests they had. This Article، using an analytical-explanatory method and printed sources، has tried to explain the reasons for the convergence and divergence between Nour al-din Mahmoud Zangi and Roman and Byzantine Saljuks.