Isachenko and Danish (b. 1895-1962) are Greek historians and researchers of the Christian Middle Ages. In 1928, they jointly published the fundamental work “History of Byzantium”. The history of Byzantium is an attempt to create a general history of the Christian church from its first beginnings to the fall of the Byzantine Empire in 1453. Own special works of researchers of the Early and Classical Middle Ages. What was common was that the works of both contained many subtle observations about the nature of the country’s spiritual life and its ideological level. From 1930-1940, research was carried out mainly by Isachenko. With his students, he continued to work on the medieval history of Byzantium, which became a kind of paradigm for other studies of this period. Therefore, the name Isachenko has become a household name to designate works on Byzantine history that claim depth and historicity. He gave the world the term stick Danishevich Isakovich, which is used in circulation “Don’t greet, but...”