In the Russo-Polish War, Polish forces invading the Ukrainian capital of Kiev attacked Bolshevik Russian troops on April 7, 1920, killing Russian soldiers in Bey Grodno, northeastern Poland, where the bodies of Russian soldiers killed in action lie on the battlefield.

   In the Russo-Polish War, Pilsudski's Polish forces invading toward the Ukrainian capital of Kiev attacked Bolshevik Russian troops on April 7, 1920. During the Polish counterattack, a Russian soldier was killed in Bey Grodno in northeastern Poland. The bodies of Russian soldiers killed in action lay on the battlefield.

　A Polish Legion was established in Galicia by Józef Pilsudski (1867-1935) to expel the Russians. Pilsudski's Polish Legion took up arms against the German and Austrian armies to liberate his native Poland from Russian rule. Pilsudski's Polish Legion was at the forefront of the Galician campaign and was the first to enter Russian territory in battle.

　After the Treaty of Brest-Litovsk after World War I, Poland was liberated from Russian forces. In accordance with the terms of the Versailles Conference, Poland established a unitary government. The first president of the Republic of Poland became Józef Pilsudski. Pilsudski crossed the long-repressed border with Russia (now the Soviet Union), and the Polish counteroffensive began on February 9, 1919, with the military occupation of vast territory.

  Pilsudski envisioned two buffer states between Poland and the Soviet Union: Belarus, with Minsk as its capital, and Ukraine, with Kiev as its capital; on April 7, 1920, Polish troops, supported by an independent Cossack army led by Ataman Petlyura, marched into the Ukrainian capital, Kiev, and conquered the city. Kiev was subsequently recaptured by the Soviet Red Army's Cossack cavalry of Budienny. Following the bulk of the Soviet forces, the Cossack cavalry set its sights on Lvov. With the prejudice of an "anti-proletarian war," the Polish army was hampered by the Western powers, and by August 13, 1920, the Russians were closing in on the Polish capital, Warsaw.

 　Russian artillery exploded on the outskirts of Warsaw. Young Polish peasants, students, and women volunteered to resist the Russian invaders with such fervor that the Polish National Army finally launched a counter-offensive as trams carrying the dead and wounded crossed the city. General Sikorski led his reserve forces north to attack the right flank of the Soviet Red Army. Marshal Pilsudski led his volunteer army to attack the Soviet Red Army's left flank from the south. Miraculously, the Soviet Red Army broke up and the Russians fled in confusion toward the border. Sikorski invaded Lithuania and occupied Vilnius.

　 An armistice was signed in October 1930. Poland annexed Volhynia, Polesije, and Podolia to Poland. The Soviet Union annexed Ukraine and Belarus and incorporated them into the Soviet Republic. However, the areas annexed by the Warsaw government were always a source of trouble. Conflicts, fueled by the Soviet Union's thirst for recapture, led to the occupation of Poland when it was partitioned by Hitler's German and Soviet forces at the end of 1939.