Although not yet fully formed the fast pace of German advance during the invasion of Poland meant that the division was dispatched to the front by 4 September 1939 and took over the task of screening the area around Różan, along the Narew river. On 5 September 1939 the German "Wodrig" Corps (1st and 12th Infantry Divisions), having broken through Polish positions in the Battle of Mława, assaulted Różan directly. Despite numerical and technical superiority, the German attacks across Narew were bloodily repelled.