The works of N.V. Pigulevskaya for the first time in world science showed Syrian culture in all its volume and completeness. She first appreciated the importance of Syrian sources for the history of the Christian church, realized and demonstrated that many cultural and ideological phenomena of the multilingual Christian world, now existing for about two thousand years, are rooted in Syrian soil. This work contains a translation and characterization of two Syrian sources - the History of John of Ephesus and the Chronicle of Zechariah Rhetor. The first part of the study focuses on the Kushan-Hephthalite states and their relationship with Iran and Byzantium. The second part of the work is related to the history of Transcaucasia. The third part of the study raises the question of Slavs and Avars.