The book of the famous Russian researcher gives a detailed description of Byzantine and Arab societies in the era of the emergence of Islam, shows the history of military-political relations between Byzantium and the Arab Caliphate in the 7th-8th centuries. and mutual cultural influences up to the 11th century. The book is written on the basis of medieval Greek (Theophanes, Nicephorus, etc.), Arab (Balazuri, Tabari, etc.), Armenian (Sebeos, Ghevond, etc.), Latin and Syrian sources used partly in originals, partly in translations.