The 'Battle of Mikołów' was a border battle between the German and Polish forces in the first stage of 'Weiss' (i) (1/2 September 1939).

The battle took place in the area of the town of Mikołów, which is located in the Polish part of Upper Silesia.

The battle began with attacks by aircraft of General Alexander Löhr’s Luftflotte IV, which bombed several areas including the airfield in Katowice. Soon after this, early in the morning of 1 September, German army formations and units crossed the German/Polish border, and received active support from members of the German minority in Poland, whose paramilitary organisation, the Freikorps, made attacks on the Polish forces rear areas. Several skirmishes took place, most of them in the densely populated industrial areas of the cities of Ruda Śląska, Chorzów and Katowice.

The German main effort was concentrated in the south of the industrial region, however, around the border towns of Mikołów and Pszczyna, where elements of the Polish Operational Group 'Silesia', which was part of Generał dywizji Antoni Szylling’s Armia 'Kraków', faced Generalleutnant Rudolf Koch-Erpach’s 8^th Division, Generalleutnant Hans von Oberstfelder’s 28^th Division and Generalleutnant Heinrich von Viettinghoff-Scheel’s 5^th Panzerdivision. All three of these formations were part of General Ernst Busch’s VIII Corps of General Wilhelm List’s 14^th Army within Generaloberst Gerd von Rundstedt’s Heeresgruppe 'Süd'.

The 5^th Panzerdivision, attacking toward Rybnik and Żory on 1 September, destroyed the Polish defenders in the morning: the formations and units which were annihilated were located in the Pszczyna forest and had constituted the connection between the Operational Group 'Silesia' and Operational Group 'Bielsko'. Their loss opened a gap in the Polish defence, which the Germans exploited on the following day. Despite desperate fighting, Generał brygady Jan Jagmin-Sadowski’s 55^th Division was wholly unable to halt the German advance.

On 2 September, the Germans preceded their main attack with an artillery bombardment from 05.00, and later in this same day two German battalions advanced on Tychy, and encountered Polish units in the area of the village of Zwakow. The battle which followed was one of the most ferocious of all those which took place during September in Upper Silesia. Polish units managed to halt the Germans, preventing them from capturing the town of Wyry. Nevertheless, during the afternoon and even though the front line had been stabilised, the headquarters of the Armia 'Kraków' ordered all units to pull back from Upper Silesia and withdraw toward Kraków and the Vistula river. This decision resulted from the fact that the Germans, attacking in the area of Woźniki, had broken the defences of the 'Kraków' Cavalry Brigade. Moreover, in the south, the Germans had also broken through the Polish positions, and Generał brygady Bernard Mond’s 6^th Division had hastily retreated toward Oświęcim. Thus, units in the area of Pszczyna and Mikołów were threatened with encirclement.

The order to withdraw had reached all Polish formations and units by 21.00 on 2 September. Most soldiers did not believe the order, but nonetheless complied with it and the whole operation was carried out in good order. Polish troops had departed Upper Silesia by 3 September, heading toward Kraków. Most of these formations and units found themselves in the area of Lublin, where they were involved in the 'Battle of Tomaszów Lubelski'.

Among the Polish formations and units which distinguished themselves in the 'Battle of Mikołów' was the 73^rd Regiment from Katowice. Comprising soldiers from Silesia, it was regarded as one of the best organised and most capable of the entire Polish army.