After heavy fights on 12 and 13 September, fought in the area of Błonie, Ołtarzew and Ożarów, the regiment crossed the Kampinos Forest and reached the Modlin Fortress. There, the regiment took part in defence of that area until the capitulation of the fortress on 29 September.
Following a series of intense battles in the Błonie, Ołtarzew, and Ożarów area from September 12-13, the regiment moved into the Kampinos Forest and arrived at the Modlin Fortress. The regiment played a defensive role there until the fortress's surrender on September 29.