Throughout the 20th century, especially in the first half, Serbian historiography had the primacy over Croatian and the population was under the influence of Serbian historiographers so Croatian historiographers could not find a fertile ground for dealing with more sensitive topics that were touching the problems of South Slavic peoples. The volunteer movement is certainly one of those sensitive topics that were exclusively dealt with by Serbian historiographers who were the main creditors of the development of the movement to the Serbs. On the issue of volunteer movement in the first half of the 20th century, Dane Hranilović was involved in his travelogue Iz zapisa jugoslavenskog dobrovoljca, Slavko Diklic, who wrote a travelogue Putničke bilješke jugoslavenskog ratnog dobrovoljca, but almost no one has dealt with the scientific way of this topic. An interesting work by Croatian historiographers is the book of George Grlica’s entitled Odessa in 1917 from Croatian perspective. A interesting book about the volunteer movement is the work of Dušan Uzelac Srbi Like kao dobrovoljci u Prvom svetskom ratu : solunski dobrovoljci, but its flaw is that it idealizes Serbian influence and discredits Croatian merits and gives too much importance to the Serbian people for the development of the volunteer movement itself. The collection of volunteer information in Odessa is located in the State Archives of Zagreb. Croatian historiographers, except Grlica, only mention the volunteer movement in the dashes, and no one focuses on the movement itself, and this diary, which is the central part of my work, is proof that the Croatians also had an important word in creating and disseminating the volunteer movement. The work is divided into two parts. Following this introduction, it follows the development of the volunteer movement, the development and emergence of the Odessa Detachment and the position of the volunteer after the First World War. The central part of the paper refers to Milan Banić's diary, which depicts his war journey until the founding of the Odessa Detachment, and at the end of the paper is a conclusion with the list of used literature.