During the Invasion of Poland in September 1939, the brigade was attached to the Kraków Army defending Lesser Poland and Silesia. Equipped with only light tanks and tankettes and without a battalion (dywizjon) of heavy artillery attached to it , which left the unit with only 8 heavier cannons, it went into battle during the first day of the German invasion. After the Battle of Jordanów Maczek's unit faced the entire German XVIII Corps of General Eugen Beyer and successfully shielded the southern flank of the Polish forces along the Beskids. Supported by several battalions of Border Guards and National Defense forces, the Polish motorized unit fought against two Panzer divisions (4th Light Division under von Hubicki and the 2nd Panzer Division under Veiel), as well as the 3rd Mountain Division under Eduard Dietl.