The world of the 20th century and, to a certain extent, the world today is the product of the First World War, its inhuman tension, its results, which then seemed unthinkable to the vast majority of those who were contemporaries and participants in the events of the first months of war. One of these eyewitnesses is the author of the diary, a Cossack officer who had the strength to keep daily notes in a combat situation and who showed remarkable civic courage by publishing these entries in 1915, a difficult year for Russia and the Russian army. The merits of the diary are undeniable. The author is observant, sincere, he not only describes what he saw and happened, but also reflects on what is happening, he has a good command of the pen, but his diary is not military journalism, which he sharply rejects. Reading the diary, we hear the living voice of a person who is not burdened with either knowledge of future events or the tasks of a war reporter.