On the first day of the Polish September Campaign, its forces counterattacked the Wehrmacht in the area of Leszno and Rawicz, together with the 25th Infantry Division.

In the following days, the Brigade, together with the whole Poznań Army, withdrew eastwards from Greater Poland.

On September 8, 1939, the cavalrymen covered the eastern wing of the Army during the outbreak of the Battle of the Bzura.

As Polish momentum weakened, on September 13 the Brigade was ordered to withdraw across the Bzura near Brochow, continuously fighting the German 4th Mountain Division of General Georg-Hans Reinhardt.

On September 18, the unit fought off attack of German 29th Motorised Division of General Joachim Lemelsen.