| 9-18 Sep 1939 | Army Poznań (led by Div. Gen. Tadeusz Kutrzeba) and Army Pomorze withdraw from Wielkopolska to engage the German army in the Battle of the Bzura, the largest battle of the September Campaign. |
|---|---|
| 8 Oct 1939 | Wielkopolska, part of Kujawy (Kuyavia) and Łódź are incorporated into the Third Reich as Reichsgau Wartheland (Polish:Kraj Warty; English: Reich Shire Warta Land). |
| 1940 | Union of Armed Struggle (Armia Krajowa [National Army] as of 14 February 1942) cells are formed in Wielkopolska. |
| 29 Jan 1945 | The combined armies of the First Belorussian Front break through the Międzyrzecz Fortified Region (MFR). |
