The Polish-Bolshevik war of 1919-1921 was the most important military conflict of the reborn Poland, and the Warsaw Battle fought in its course - perhaps the greatest Polish military success in the history of the 20th century. It is worth adding that from its beginning, until the beginning of the summer of 1920, the Polish side was the attacking party, shifting its influence decidedly to the east - at its peak, all the way to Kyiv. In its course, attempts were also made to implement the so-called the federalist concept of the Polish eastern border. However, from June-July 1920, in connection with the huge offensive of the Red Army under the command of Mikhail Tukhachevski, the Polish side was pushed to the defensive and to the defense in the suburbs of Warsaw. In this difficult situation, Józef Piłsudski, the head of state, remained calm and managed to carry out the so-called counterattack from the Wieprz River, which forced the Soviet troops to retreat. The success of the Battle of Warsaw was later repeated in the course of the German operation. Finally, the war ended in 1921 with the signing of the peace treaty in Riga, which regulated the Polish-Soviet border until September 17, 1939. It is worth adding that in this armed conflict, the nascent Polish Army was heterogeneous, consisting of units of very different provenance, among them - soldiers of the Polish Legions, the Blue Army, the Greater Poland army and recruits recruited in 1919 and 1920. Also, the equipment, equipment and tactics of individual units were often very different. It is assumed that theoretically, the position of the Polish infantry division from 1919-1921 consisted of the command, two infantry brigades (two infantry regiments each), artillery brigade, sapper battalion, cavalry squadron, telegraph company and caravans. But, for example, the infantry divisions of the Blue Army had a structure based on three infantry regiments, and in the case of the so-called Instructional Division - by five regiments. Therefore, it is virtually impossible to give a uniform structure of the Polish infantry division in the years 1919-1921. It is worth adding, however, that at the peak of hostilities, the Polish side deployed about 1.1 million soldiers, a number similar to that of the September 1939 campaign.