ENIn three books (1972, 1982 and 2010) that were compiled using the Correlates of War (COW) project as their basis, the uprising of 1830–1831 is referred to as the ‘First Polish War of 1831’. As mentioned in the preface, this name should come as no surprise, as it was not then the practice to distinguish Lithuania as a separate geopolitical unit. At that time, it was not uncommon for all of the former Polish-Lithuanian Commonwealth, which was partitioned by Russia, Austria and Prussia at the end of the eighteenth century, to simply be called ‘Poland’. However, on reading the more detailed narrative of this war presented in the 2010 book, one is forced to acknowledge that the compilers of the data collection held to the more narrow understanding of Poland as a geopolitical unit and identified it with the Polish Kingdom, which was subordinate to the Russian Empire at that time. The significant circumstance that the war had spread not only throughout the Polish Kingdom, but also to the former Grand Duchy of Lithuania (hereinafter – Lithuania), was thus overlooked. No reference is made at all to the uprising that began independently in Lithuania in March 1831 and which joined the uprising that began in the Polish Kingdom in November 1830; the battles that were fought in Lithuania by local rebels and corps of the Polish regular army are also neglected. So, in essence, it is not the entire war that is described, but only parts thereof, which, of course, does not contribute to the accurate and comprehensive itemizing of the nature of this war and the losses experienced by the warring sides. Information about military action in Lithuania is completely left out in the description of this war.In the abundant historiography of the war, we will not find any significant doubt that the uprising in Lithuania was an integral part of the insurrection that began in the Polish Kingdom, or that the rebels were fighting for the common goal of liberation from Russia and the restoration of the former state – the Polish-Lithuanian Commonwealth. This chapter of the book is therefore dedicated to liquidating this obvious omission and, based on historiographical material and additional research, to clarifying and identifying the quantitative and qualitative parameters of the uprising that took place in Lithuania in 1831 in accordance therewith. It should be noted that historiography of the 1830–1831 uprising in Lithuania is quite extensive, written over nearly two centuries by various authors and in various languages. Practically as soon as the weapons had fallen silent, memoirs of witnesses and participants of the uprising emerged, and researchers from various countries set to work; this process continues to this day. The course, strategies and tactics of military operations have been elucidated in detail, and the armed forces of the contending parties have been described, yet thus far, little attention has been given to the topic of losses suffered by the warring sides. Nevertheless, more detailed information about the Lithuanian fighters who were killed in the battles of this war, as well as officers and soldiers of the Polish corps and Russian military units, can be found in works by Alexander Puzyrewski, Wacław Tokarz, Olga Gorbacheva, Jan Ziółek, and Jacek Feduszka. One of the most comprehensive pieces dedicated to examining the uprising that took place in Lithuania is Feliksas Sliesoriūnas’s monograph, which presents a considerable amount of concrete data about the course of military action in Lithuania.This has become a pivotal point in continuing further studies, because it includes detailed descriptions of the movement of enemy military units and the course of battles, as well as lists of battle casualties: those who were killed, wounded and taken prisoner. However, the author neither provided data that summarizes the battle circumstances resulting in fatalities, nor evaluated the credibility of information provided in primary sources in more depth. In order to present the most accurate and objective information possible on the people killed from both warring sides in battles that took place within the territory of the former Grand Duchy of Lithuania, material safeguarded in the Russian State Military Historical Archive was reviewed. This includes documentation of Russian military authorities, reports of commanders of military units that fought in Lithuania, communiqués, and military operation journals that include data regarding casualties. New material previously unused in Lithuanian historical literature on the rebels of the Augustów Voivodeship has been found at the Central Archives of Historical Records in Warsaw; this material reflects the course of the uprising in Lithuanian districts. New material related to the assessment of military action in Lithuania has been found in the Manuscripts Department at the University of Warsaw Library. Therefore, based on the works of the above-mentioned historians, and upon reviewing known and new primary sources, opportunities emerged to carry out a new investigation of the uprising in Lithuania [p. 33-35].