20th Infantry Division () was an

infantry Infantry, or infantryman are a type of soldier who specialize in ground combat, typically fighting dismounted. Historically the term was used to describe foot soldiers, i.e. those who march and fight on foot. In modern usage, the term broadl ...

division of the

Polish Army The Land Forces () are the Army, land forces of the Polish Armed Forces. They currently contain some 110,000 active personnel and form many components of the European Union and NATO deployments around the world. Poland's recorded military histor ...

during the

interbellum period In the history of the 20th century, the interwar period, also known as the interbellum (), lasted from 11 November 1918 to 1 September 1939 (20 years, 9 months, 21 days) – from the end of World War I (WWI) to the beginning of World War II ( ...

, which took part in the

Polish September Campaign The invasion of Poland, also known as the September Campaign, Polish Campaign, and Polish Defensive War of 1939 (1 September – 6 October 1939), was a joint attack on the Republic of Poland by Nazi Germany, the Slovak Republic, and the Soviet ...

. It was formed in 1920 from the reorganization of the 2nd Lithuanian-Belarusian Division. Stationed in

Baranavichy Baranavichy or Baranovichi is a city in the Brest Region of western Belarus. It serves as the administrative center of Baranavichy District, though it is administratively separated from the district. As of 2025, it has a population of 170,817. ...

() and commanded by Colonel

Wilhelm Lawicz-Liszka Wilhelm Lawicz-Liszka was a Polish infantry officer of the Polish Legions in World War I and the Blue Army, a colonel of the Polish Armed Forces and the Polish Armed Forces in the West. He fought for Polish independence in World War I and World ...

September 1939 Campaign

In the summer of 1939 it was moved west and became part of the

Modlin Army Modlin Army () was one of the Polish armies that were part of the Polish defense against the German Invasion of Poland. After heavy casualties in the battle of Mława (September 1–3), the Army was forced to abandon its positions near Warsaw arou ...

. Its task was to defend the partly fortified area north of

Mława Mława (; ''Mlave'') is a town in north-eastern Poland with 30,403 inhabitants in 2020. It is the capital of Mława County. It is situated in the Masovian Voivodeship. During the invasion of Poland in 1939, the battle of Mława was fought to the ...

, near the interwar border of Poland and

East Prussia East Prussia was a Provinces of Prussia, province of the Kingdom of Prussia from 1772 to 1829 and again from 1878 (with the Kingdom itself being part of the German Empire from 1871); following World War I it formed part of the Weimar Republic's ...

. Between September 1 and 3, 1939 (see:

September Campaign The invasion of Poland, also known as the September Campaign, Polish Campaign, and Polish Defensive War of 1939 (1 September – 6 October 1939), was a joint attack on the Republic of Poland by Nazi Germany, the Slovak Republic, and the Sovie ...

), the division defended positions around Mława in the

Battle of Mława The Battle of Mława, otherwise known as the Defence of the Mława position, took place to the north of the town of Mława in northern Poland between 1 and 3 September 1939. It was one of the opening battles of the Invasion of Poland (1939), Inv ...

, facing the more numerous and better equipped units of the German I Army Corps (composed of: 11th Infantry Division, 61st Infantry Division and the

Panzer Division Kempf The Panzer Division "Kempf" (, also ''East Prussia Panzer Formation'' (de: ''Panzerverband Ostpreußen'') was an ''ad hoc'' combined arms formation consisting of regular German Army personnel and SS. It was created for operations out of East Pr ...

). The

Wehrmacht The ''Wehrmacht'' (, ) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the German Army (1935–1945), ''Heer'' (army), the ''Kriegsmarine'' (navy) and the ''Luftwaffe'' (air force). The designation "''Wehrmac ...

was advancing southwards, towards

Warsaw Warsaw, officially the Capital City of Warsaw, is the capital and List of cities and towns in Poland, largest city of Poland. The metropolis stands on the Vistula, River Vistula in east-central Poland. Its population is officially estimated at ...

, but first attacks were repulsed with the loss of around 25 German tanks. Unable to capture Mława in frontal attack, the Germans decided to go around and attack from sides. As they threatened 20th I.D.'s rear, the Poles were ordered to withdraw. However, supported by the neighbouring Polish 8th Infantry Division, the defenders kept their positions. On September 2, German attacks failed again, even though they ordered Polish civilians to walk in front of their tanks. The Germans decided to organize an offensive from the area of

Ostrołęka Ostrołęka (; ) is a small city in northeastern Poland on the Narew river, about northeast of Warsaw, with a population of 51,012 (2021) and an area of . It is the capital of both Ostrołęka County and Ostrołęka City County in the Masovian V ...

and

Przasnysz Przasnysz () is a town in north-central Poland. Located in the Masovian Voivodship, about north of Warsaw and about south of Olsztyn, it is the capital of Przasnysz County. It has 18,093 inhabitants (2004). It was one of the most important towns ...

. This succeeded, and on September 3, Polish positions were broken. To make matters worse, the counter-attack of the 8th I.D. was ill-organized and failed, resulting in chaotic, panic withdrawal of 8th I.D. units. Facing the difficult situation, the 20th I.D. was ordered to withdraw on the night of September 3–4. Bombed by the Germans, the division around September 7 reached the area of

Płock Płock (pronounced ), officially the Ducal Capital City of Płock, is a city in central Poland, on the Vistula river, in the Masovian Voivodeship. According to the data provided by Central Statistical Office (Poland), GUS on 31 December 2021, the ...

. Then, the unit's remains entered Warsaw, helping with its defence from northwest. They capitulated together with the Warsaw garrison on September 28 (see:

Siege of Warsaw (1939) The siege of Warsaw in 1939 was fought between the Polish Army, Polish Warszawa Army, Warsaw Army () garrisoned and entrenched in Warsaw and the invading German Army (Wehrmacht), German Army.Zaloga, S.J., 2002, ''Poland 1939'', Oxford: Osprey Pu ...

). The Germans who fought against the 20. at Mława gave it a nickname "

Steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

Division."

Order of Battle (1939)

* Division Headquarters - based in

() * - based in Baranavichy * - based in

Slonim Slonim is a town in Grodno Region, in western Belarus. It serves as the administrative center of Slonim District. It is located at the junction of the Shchara and Isa (river), Isa rivers, southeast of Grodno. As of 2025, it has a population of ...

() * - based in Slonim * - based in

Pruzhany Pruzhany is a town in Brest Region, Belarus. It serves as the administrative center of Pruzhany District. The town is located at the confluence of the Mukha River and the Vets Canal, where the Mukhavets River rises. As of 2025, it has a popu ...

()

References

20th Military units and formations established in 1920 1920 establishments in Poland 20th {{mil-unit-stub

September 1939 Campaign

Order of Battle (1939)

See also

References