Military history of Poland during World War II

In World War II, the Polish armed forces were the fourth largest Allied forces in Europe, after those of the Soviet Union, United States and Britain.[a] Poles made substantial contributions to the Allied effort throughout the war, fighting on land, sea, and in the air. Polish forces in the east, fighting alongside the Red army and under Soviet high command, took part in the Soviet offensives across Belarus and Ukraine into Poland and across the Vistula and Oder Rivers to the Battle of Berlin.

Source: Wikipedia — Military history of Poland during World War II (CC BY-SA 4.0)