The 'Battle of Lwów' was the Polish attempt to hold the city of Lwów in south-western Poland against German forces advancing from the west and Soviet forces advancing from the east anxious to eliminate this key to the 'Romanian bridgehead' (12/22 September 1939).

The Poles had initially decided that the city was not to be defended as it was considered to be too deep behind the Polish lines and too important to Polish culture to be jeopardised for military purposes. However, the speed of the 'Weiss' (i) invasion and the almost-complete disintegration of the Polish reserve Armia 'Prusy' after the 'Battle of Łódź' left the city in danger of German assault. On 7 September 1939, therefore, Generał brygady Władysław Langner started to organise the defence of the city. As a first step, the Polish forces were to defend the line linking Bełżec, Rawa Ruska and Magierów against the German advance. Generał dywizji Rudolf Prich was given command of the all the Polish forces in the area, and on 11 September prepared a plan to defend the area. The Polish units were to defend the line of the San river, with defensive strongpoints along the line linking Żółkiew, Rawa Ruska, Janów (also called Yaniv or Ivano-Frankove) to the west of the river, Wereszycą and Gródek Jagielloński.

On the following day, the first German motorised elements arrived in the area under the command of Oberst Ferdinand Schörner, commander of the 98^th Gebirgsjägerregiment: these elements were the advance guard of Generalleutnant Ludwig Kübler’s 1^st Gebirgsdivision within Generaloberst Gerd von Rundstedt’s Heeresgruppe 'Süd'. After they had captured Sambor, some 41 miles (66 km) from Lwów, Schörner ordered his units to break through the weak Polish defences and take the city as rapidly as possible.  The assault group was composed of two motorised infantry companies and one battery of 150-mm (5.91-in) guns. The group outflanked the Polish defenders and reached the outskirts of the city, but was then bloodily repelled by the numerically inferior Polish defenders. The Polish commander of the sector had only three infantry platoons and two 75-mm (2.95-in) guns, but his force was soon reinforced and held its positions until dawn. The same day, command of the city’s defence was passed to Generał brygady Franciszek Sikorsky, a veteran of World War I and the Polish-Soviet War.

On the next day, Schörner’s main force arrived, and at 14.00 the Germans broke into the city centre before again being driven back after heavy city fighting with Polish infantry units formed of local volunteers and refugees. To strengthen the Polish defences, Generał broni Kazimierz Sosnkowsky departed Lwów for Przemyśl, farther to the west, on 13 September and assumed command of a group of Polish formations and units which were to break through the German lines and reinforce the city.

Schörner decided to fall back and encircle the city while he awaited reinforcement. His force achieved a limited success and captured the important suburb of Zboiska and the surrounding hills. However, the Polish forces were now reinforced with units that had been withdrawn from central Poland as well as new volunteer units formed within the city. In addition, the Polish 10^th Motorised Brigade, under Pułkownik Stanisław Maczek, arrived and in heavy fighting started to retake Zboiska. The suburb was indeed recaptured, but the surrounding hills remained in the hands of the Germans and provided them with good fields of vision over the city centre. Schörner placed his artillery there to shell the city. In addition, the city was almost constantly bombed by the Luftwaffe. Among the main targets for the German air and artillery attacks were prominent buildings, such as churches, hospitals, the water treatment plant and powerplants.

On 17 September, the USSR declared all pacts with Poland null and void on the basis that the Polish state had ceased to exist, and took the opportunity to join Germany in the dismemberment and occupation of Poland. The forces of Komkor Filipp I. Golikov’s 6^th Army of Komandarm 2a ranga Semyon K. Timoshenko’s Kiev Special Military District crossed the border just to the east of Lwów at the start of a high-speed advance toward the city. Involving Komdiv Fedor Ya. Kostenko’s II Cavalry Corps (two cavalry divisions and one light tank brigade) and the 10^th Tank Brigade of Komdiv Konstantin S. Kolganov’s XVII Corps, the Soviet invasion made all the Polish plans to defend the 'Romanian bridgehead' irrelevant, and the Polish commander decided to withdraw all of his units to the close perimeter and thus defend only the city rather than the whole area: this concentration strengthened the Polish defences. On 18 September, the Luftwaffe dropped thousands of leaflets over the city to urge the Poles to surrender, but this blanishment was ignored. The Germans then began a general assault on the city, but was once again repulsed.

The Soviet intervention on 17 September also made necessary some changes in the German plan. Early in the morning of 19 September, the first Soviet armoured units reached the city’s eastern outskirts and the suburb of Łyczaków. After a short fight, the Soviet units were pushed back. However, the arrival of the Soviet forces completed the encirclement of the city overnight and linked with the German forces besieging Lwów from the west.

The Polish defences were composed mainly of field fortifications and barricades constructed by residents under supervision of military engineers. Sikorsky ordered an organised defence of the city’s outer perimeter, where defences were readied in some depth. During the morning of 19 September, the first Soviet envoys arrived and began negotiations with the Polish commanders. Polkovnik Ivanov, the commander of a tank brigade, told Pułkownik Bronisław Rakowski that the Soviets had entered Poland to help it fight the Germans and that the major priority for his units was to enter the city.

On this same day, Schörner also sent an envoy and demanded that the city be surrendered to his troops. When the Polish envoy replied that he had no intention of signing such a document, he was informed that a general assault had been ordered for 21 September and that the city would most certainly be taken. However, Adolf Hitler’s pull-back order of 20 September then instructed von Rundstedt to leave the capture of Lwów to the Soviets. The attack planned for implementation by General Eugen Beyer’s XVIII Corps of Generaloberst Wilhelm List’s 14^th Army for 21 September was then cancelled, and the German corps prepared to move back to the west of the line of the Vistula and San rivers. On the following day, Sikorsky decided that the situation of his forces was hopeless:while reserves, human resources and matériel were still plentiful, Sikorsky appreciated that the continued defence of the city would be fruitless and result only in more civilian casualties. He therefore decided to start surrender talks with the Soviets.

During the morning of 22 September, the act of surrender was signed in the suburb of Winniki. The Soviets accepted all of the conditions proposed by Langner. The All Polish other ranks were to leave the city, register themselves with the Soviet authorities and then be allowed to go home. Officers would be allowed to keep their belongings and leave Poland for whichever country would accept them. The Soviet forces then entered the city and the Soviet occupation began. The Soviets broke the terms of surrender shortly after 12.00 when the NKVD began arresting all Polish officers. They were escorted to Tarnopol, whence they were sent to various prison camps in the USSR, mostly to the infamous camp in Starobielsk. Most of the officers, including Sikorsky, were murdered in 1940 in what became known as the Katyn Massacre.