The 61st Infantry division was created just before the outbreak of conflict and took part in the invasion of Poland on 1 September 1939 as part of von Küchler's 3rd Army under Army Group North. It engaged in heavy fighting at the Battle of Mława, afterwards crossing the Narew River near Pułtusk. Fighting its way across the Bug River, it approached the Polish capital at Warsaw on 18 September and remained in the vicinity until the end of the campaign.