The 'Battle of Jarosław' was a German and Polish battle within 'Weiss' (i) for the Polish city of Jarosław on the San river (10/11 September 1939).

During the battle the Polish forces of Pułkownik Stanisław Maczek held the river crossings in the town for two days against German forces, buying the time for the Polish 10^th Motorised Cavalry Brigade to cross the river and retreat farther to the east.

Unlike most other Polish armies during the German invasion of September 1939, Generał dywizji Antoni Szylling’s 'Kraków' Armia managed to withstand the initial German assault on Silesia and retreat steadily to the east. The Carpathian mountains in the south and the Vistula river to the north provided enough flank protection for the army to concentrate on the fighting of actions to delay General Walter von Reichenau’s 10^th Army in Generaloberst Gerd von Rundstedt’s Heeresgruppe 'Süd'. However, the numerical and technical superiority of the German forces meant that the Polish forces were too weak to counterattack, so the best choice for the 'Kraków' Armia was to hold the numerous river lines and major towns of the area and thereby facilitate the eastward retreat of the Polish forces.

One such line was readied along the San river by General brygady Wacław Scewola-Wieczorkiewicz, the pre-war commanding officer of the Przemyśl-based X Corps Area, one of the Polish army’s peacetime formation. The preparations started on 7 September, but as most of the forces in the area were already mobilised and most mobile infantry battalions were sent to the front, the defensive positions along the rivers were severely undermanned. On the following day, in the area between Przemyśl and Rozwadów, the Polish commander had only 10 infantry battalions, one engineer battalion and 42 pieces of artillery at his disposal. The central sector of the line around Jarosław, between Radymno and Sieniawa, was manned by four infantry battalions and 20 pieces of artillery under the command of Podpułkownik Jan Wójcik of Pułkownik Edward Dojan-Surówka’s 2^nd Legions Division. The force was insufficient to hold the river line, all the more so as the summer of 1939 was uncommonly dry and the level of water in Polish rivers was very low, allowing the German armoured forces to cross them by fording.

At the same time, Generalmajor Dr Alfred Ritter von Hubicki’s 4^th leichte Division and Generalleutnant Rudolf Veiel’s 2^nd Panzerdivision of General Eugen Beyer’s XVIII Corps of General Wilhelm List’s 14^th Army were approaching Jarosław from the north-west with the task of crossing the river and thereby cutting off the retreating 'Kraków' Armia from the east. During the night of 10 September, the 4^th leichte Division moved from the area of Rzeszów through Pruchnik and Zamiechów to Radymno on the San river, and early in the morning the Germans took the Polish defenders by surprise and crossed the river unopposed.

Around the same time Maczek arrived at Jarosław. His 10^th Motorised Cavalry Brigade was one of only two fully motorised Polish units and had been used by the 'Kraków' Armia as an 'firefighting' unit, committed to battle each time the German or Slovak forces tried to outflank the considerably slower Polish army. This time his unit formed the rearguard of the army and was to provide cover for the retreating formations and unit. Maczek decided to station his brigade around Jarosław and strengthen the Polish defences there.

Around noon the two German divisions arrived near Jarosław and the Polish front guards retreated to the other side of the river, leaving only a token infantry force under Colonel Wójcik at the bridgehead on the western banks. Maczek decided to hold the city for one day in order to provide a safe fallback position for the slower units following his brigade. After that his unit was to continue its pursuit of his army and organise another delaying action farther to the east near Lwów.

In the early afternoon the Germans started their assault on the city, but were repelled and forced to leave several damaged or destroyed tanks on the battlefield. The repeated assaults later that day were also unsuccessful. During the night that followed, Maczek decided that his plan had succeeded but also that continued defence of the city could result in his brigade being cut off from the rear by the German forces advancing from Radymno. Maczek therefore moved his brigade farther to the east in the direction of the Oleszyce-Lubaczów area. Podpułkownik Wójcik’s forces were now to hold the town for as long as possible, and then follow the motorised brigade. The Poles blew the bridges and left only a token force in the city, while most of their men retreated under the cover of darkness. Early in the morning of 11 September the Germans resumed their assault, this time prefaced by a heavy artillery barrage. However, since most of the Polish units were already miles away, the losses inflicted were negligible. At about 12.00, the German armour rolled toward the Polish positions only to discover that the several infantry companies of an infantry battalion, which had been holding the Polish positions, had also withdrawn.