On September 9, General Wiktor Thommee ordered the division to retreat behind the Rawka river. On the next day, the order was changed and the division marched towards Warsaw, via Pruszkow. Despite initial successes, it failed to break through German positions. As a result, the division made an attempt to reach the fortress of Modlin. After entering the complex, it took part in the Battle of Modlin, until the capitulation on September 29.