The Battle of Grodno took place between 21 September and 24 September 1939, during the Soviet invasion of Poland. It was fought between improvised Polish units under Gen. Wacław Przeździecki and Soviet Red Army troops of Komkor Ivan Boldin's Dzerzhinsky Cavalry Mechanized Group, at the time in a non-aggression agreement with Nazi Germany under the Ribbentrop-Molotov Pact.
The Soviet aggression caught much of the eastern Poland virtually undefended, as most of the Polish forces from the area had already been transferred to the German front. After breaking through overstretched defences of the Border Defence Corps, the Soviet 15th Tank Corps started a fast advance towards the city of Grodno. Commander of the pre-war Grodno Military Area Command Gen. Józef Olszyna-Wilczyński, together with the mayor of Grodno Roman Sawicki, started organizing city defences, based mostly on march battalions, volunteers, Boy Scouts and police forces.