On 1 September 1939, the "Wehrmacht" invaded Poland. I./StG 2 began the invasion with 37 combat ready aircraft from 38. On the first day, I "Gruppe" bombed Wieluń, with other elements of the wing. The StG 76 and 77 were also involved in the bombing against the undefended town which may have occurred when faulty intelligence reports asserted the existence of a Polish cavalry formation was present.Kraków, Katowice and Wadowice were bombed by the group on the first day of the invasion.