[4] The 3rd Army saw its first action in September 1939, taking part in the operation in Belarus and Poland.
The invasion was conducted under the terms of the Molotov–Ribbentrop Pact, which divided Poland between the Soviet Union and Nazi Germany and guaranteed that neither country would attack the other.
[6] The 3rd Army took part in the operations of the Western, Central, Bryansk during the defenses of Grodno, Lida, and Novogrudok.
During the second half of the Eastern Front, the 3rd Army took part in the Battle of Kursk, where numerically superior Soviet forces, using anti-tank defenses, defeated the German forces, thus stopping Operation Zitadelle and robbing the German Army of all hopes of victory on the Eastern Front.
During the final phases of the war, the 3rd Army took part in Operation Bagration, the East Prussian Offensive, and the advance into eastern Germany, where it participated in the Battle of Berlin.