[1] However, the speed of the Nazi invasion and the almost-complete disintegration of the Polish reserve Prusy Army after the Battle of Łódź resulted in the city being in danger of a German assault.

[2] The following day, the first German motorised units under Colonel Ferdinand Schörner, 1st Mountain Division (Wehrmacht), arrived in the area.

[4] The Polish commander of the sector had only three infantry platoons and two 75 mm guns, but his forces were soon reinforced and held their positions until dawn.

In addition, the Polish 10th Motorised Brigade, under Colonel Stanisław Maczek, arrived and started the heavy fighting to take back the suburb of Zboiska.

The town was recaptured, but the surrounding hills remained in German hands and gave a good view of the city centre.

[3]: 83  The forces of the 6th Red Army of the Ukrainian Front, under Filipp Golikov, crossed the border just east of Lwów and started a quick march towards the city.

In the early morning of September 19, the first Soviet armoured units reached the eastern outskirts of the city and the suburb of Łyczaków.

However, the Soviet forces completed the encirclement of the city overnight and linked with the German army besieging Lwów from the west.

The Polish defences were composed mainly of field fortifications and barricades constructed by the local residents under supervision of military engineers.

When the Polish envoy replied that he had no intention of signing such a document, he was informed that a general assault was ordered for September 21 and that the city would most surely be taken.

Hitler's evacuation order from September 20 instructed Gerd von Rundstedt to leave the capture of Lwow to the Soviets.

Sikorski had approximately 11 infantry battalions, 5 batteries of artillery (mainly 75 mm guns), cavalry unit, engineering platoon and a small number of soldiers who had retreated into the city.