The book by the French historian Ferdinand Chalandon (1875–1921) is dedicated to the period of the reign of Emperor Alexios I Komnenos (1081–1118), the first emperor of the Komnenos dynasty. Based on a large amount of factual material, this work still remains the only summary work on the initial period of the reign of the Komnenos, and therefore deserves attention. As the founder of a new dynasty, Alexei I gave Byzantine politics the direction that it maintained throughout the entire 12th century. His reign opened a new era in the history of relations between East and West. The direct merit of F. Chalandon is the development of the actual history of Byzantine politics in Asia Minor and the reconstruction of the chronology of the entire period of the reign of Alexei I. Based on an analysis of all the information available to the scientist, he reconstructed the dating of the wars of this emperor with the Italian Normans, with the Pechenegs and Cumans on the Balkan Peninsula, with the Iconian Sultanate and individual emirates of the Seljuk Turks in Asia Minor. The book also scrupulously analyzes the foreign policy of the Byzantine Empire, in particular, it reconstructs the chronology of the relationship between Alexei Komnenos and the leaders of the First Crusade.