The Battle of Kampinos Forest was in fact a series of skirmishes and battles fought in the forests around Kampinos during the Invasion of Poland of 1939, between the Polish Army and the German Wehrmacht.
Between 9 and 20 September, the remnants of the Polish forces fighting in the battle of Bzura were withdrawing through the large forest complex towards Warsaw and the Modlin Fortress. The earlier route was adopted by the Poznań Army under Gen. Władysław Bortnowski, while the latter by the forces of the Pomorze Army under Gen. Wiktor Thommee. At the same time the German Wehrmacht tried to cut the Polish forces out by assaulting the forests both from the north and from the south.
Although most of the Polish forces finally broke through in the aftermath of the battle of Wólka Węglowa, both sides suffered heavy casualties.