On 9 September, Bortnowski subordinated the Pomeranian Army under the Poznań Army led by General Tadeusz Kutrzeba. Next, the combined forces of the Pomeranian and Poznań Armies took part in the Battle of the Bzura, a counter-offensive devised by Kutrzeba. Bortnowski's forces were most notable for fighting near the outskirts of Łowicz and Sochaczew.