In Wielkopolska, population ratios were altered with large-scale evictions of Polish families and an influx of German settlers from other parts of eastern Europe. Administrative realities and even regional conditions were different. In Wielkopolska, it was impossible to develop an underground on the same scale as in central Poland, let alone form guerrilla groups or take up armed struggle.

A successful campaign to burn down German warehouses in the Poznań river port, known as “Operation Bulwark” was waged in February 1942. Once the National Army (AK) was set up in Wielkopolska, the AK Western Regional Command operated under nine inspectorates: Poznań, Ostrów Wielkopolski, Środa Wielkopolska, Leszno, Gniezno, Wągrowiec, Nowy Tomyśl, Szamotuły and Krotoszyn. In January 1944, the Gestapo ransacked the headquarters of the Poznań District AK and arrested its commander, Col. Henryk Kowalówka.

The best known Polish underground group during the Nazi occupation was that led by Dr. Franciszek Witaszek. This was made up of doctors and laboratory technicians who prepared substances for sabotage purposes, including toxic compounds that would trigger fatal pathological processes. These means was used to kill German civil servants and Gestapo offers who were particularly threatening to the Polish resistance movement. The laboratory technicians also produced corrosive substances and thermite bombs to induce fires in German transports. Dr Witaszek’s group was exposed in April 1942 and virtually all of them were arrested by the Gestapo. They were executed on 8 January 1943 after an arduous investigation. Their bodies were incinerated while their heads served as “exhibits” for the students at the Poznań Reich University for the next three years. Some of them were identified after WWII (Franciszek Witaszek, Henryk Günther, Sonia Górzna and Helena Siekierska) and ceremonially buried on the slopes of the Poznań Citadel.