Abstract: This article analyzes a little-known book by Michael Stepanov devoted to the military actions of the Ruschuk Detachment under the command of the Successor Tsesarevich Alexander Alexandrovich during the Russo-Turkish War of 1877–1878. The book, published on the tenth anniversary of the end of the war and has not been republished since, is a comprehensive systematic review of the unit’s participation in military operations. The author of the work, an officer of the Russian General Staff, was a direct participant in the events that took place, since during the war he was seconded to the headquarters of the Ruschuk Detachment. The use of the method of archive source analysis allows us to identify the features of Michael Stepanov’s book and his author’s style, the significance of the work as a source on the history of the Russo-Turkish war. In the course of the conducted research, it was found that this book contains a detailed, systematic and highly qualified review of the actions of the Ruschuk Detachment during the war. An analysis of Michael Stepanov’s work shows that the book in its genre is not a memoir literature, but a military historical essay. The author is characterized by an objective approach to describing events, the absence of protruding his own role, moreover, he mentions himself extremely rarely and exclusively in the third person. Michael Stepanov’s book is being studied for the first time, despite its undoubted importance for analyzing the combat path of such a famous unit of the Russian Danube Army as the Ruschuk Detachment, which played a significant role in ensuring Russia’s victory in the Balkan theater of operations. Michael Stepanov’s work, based on a wide source base, remains relevant to this day for a comprehensive study of the Russo-Turkish War of 1877–1878.