Soviet invasion of Poland

1939 complex military operation performed by the USSR on the Second Polish Republic

The 1939 Soviet invasion of Poland was a Soviet military operation that started without a formal declaration of war on 17 September 1939. It was during the early stages of World War II. Sixteen days after Nazi Germany invaded Poland from the west, the Soviet Union did so from the east. The invasion ended on 6 October 1939. Germany and the Soviet union divided the whole of the Second Polish Republic.[8]

Soviet invasion of Poland
Part of the invasion of Poland in World War II
Soviet invasion on Poland 1939.jpg
Soviet forces marching through Poland in 1939.
Date17 September – 6 October 1939
Result Decisive Soviet victory
Polish territory divided and annexed
Poland  Soviet Union
Commanders and leaders
Flag of Poland.svg Edward Rydz-Śmigły Soviet Union Kliment Voroshilov (Commander-in-Chief)
Soviet Union Mikhail Kovalyov (Belarusian Front)
Soviet Union Semyon Timoshenko (Ukrainian Front)

20,000 Border Protection Corps,[1]

250,000 Polish Army.[3][4]

466,516–800,000 troops[3][5]

33+ divisions
11+ brigades
4,959 guns
4,736 tanks
3,300 aircraft
Casualties and losses

3,000–7,000 dead or missing,[1][6]

up to 20,000 wounded.[1][Note 1]
1,475–3,000 killed or missing
2,383–10,000 wounded.[Note 2]

In early 1939, the Soviet Union asked the United Kingdom, France, Poland, and Romania to make an alliance against Nazi Germany. The Soviet Union wanted Poland and Romania to let Soviet troops go through their territory.[9] Poland and Romania both said no. The Soviet Union made a secret deal with Nazi Germany on 23 August. They planned to divide Northern and Eastern Europe into German and Soviet lands.[10] One week later, German forces invaded Poland from the north, south, and west. Polish forces then withdrew to the southeast to wait for French and British support. The Soviet Red Army invaded the Kresy on 17 September.[11][12] The Soviet government said it was acting to protect the Ukrainians and Belarusians. They lived in the eastern part of Poland.[13][14][15]

The Soviet government added the land they won. In November 1939 they made the 13.5 million formerly Polish citizens become citizens of the Soviet Union. They sent hundreds of thousands of people from this region to Siberia and other remote parts of the Soviet Union.

Soviet forces stayed in eastern Poland until the summer of 1941. They were moved by the invading German army in the course of Operation Barbarossa. The area was under Nazi occupation until the Red Army reconquered it in the summer of 1944. An agreement at the Yalta Conference let the Soviet Union add almost all of their part of the Second Polish Republic. The People's Republic of Poland got the southern half of East Prussia and lands east of the Oder-Neisse Line.[16] The Soviet Union added the lands into the Ukrainian Soviet Socialist Republic and the Byelorussian Soviet Socialist Republic.[16]


  1. The figures do not take into account the approximately 2,500 prisoners of war executed in immediate reprisals or by anti-Polish Organization of Ukrainian Nationalists.[1]
  2. Soviet official losses – figures provided by Krivosheev – are currently estimated at 1,475 KIA or MIA presumed dead (Ukrainian Front – 972, Belorussian Front – 503), and 2,383 WIA (Ukrainian Front – 1,741, Belorussian Front – 642). The Soviets lost approximately 150 tanks in combat of which 43 as irrecoverable losses, while hundreds more suffered technical failures.[5] Sanford indicates that Polish estimates of Soviet losses are 3,000 dead and 10,000 wounded.[1] Russian historian Igor Bunich estimates Soviet losses at 5,327 KIA or MIA without a trace and WIA.[7]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Sanford pp. 20–24
  2. Increasing numbers of Border Protection Corps units, as well as Polish Army units stationed in the East during peacetime, were sent to the Polish-German border before or during the German invasion. The Border Protection Corps forces guarding the eastern border numbered approximately 20,000 men.[1]
  3. 3.0 3.1 "Kampania wrześniowa 1939" [September Campaign 1939]. PWN Encyklopedia (in Polish). Archived from the original on 9 May 2006. Retrieved 16 July 2007.
  4. The retreat from the Germans disrupted and weakened Polish Army units, making estimates of their strength problematic. Sanford estimated that approximately 250,000 troops found themselves in the line of the Soviet advance and offered only sporadic resistance.[1]
  5. 5.0 5.1 Krivosheev, Grigory Fedot (1997). Soviet casualties and combat losses in the twentieth century. London: Greenhill Books. ISBN 1-85367-280-7.
  6. Topolewski & Polak p. 92
  7. Bunich, Igor (1994). Operatsiia Groza, Ili, Oshibka V Tretem Znake: Istoricheskaia Khronika. VITA-OBLIK. p. 88. ISBN 5-85976-003-5.
  8. Gross pp. 17–18
  9. Watson p. 713
  10. Watson p. 695–722
  11. Kitchen p. 74
  12. Davies (1996) p. 440
  13. "The German Ambassador in the Soviet Union, (Schulenburg) to the German Foreign Office No. 371". Avalon project. Lillian Goldman Law Library. Retrieved 2009-06-11.
  14. "The German Ambassador in the Soviet Union, (Schulenburg) to the German Foreign Office No. 372". Avalon project. Lillian Goldman Law Library. Retrieved 2009-06-11.
  15. Degras pp. 37–45
  16. 16.0 16.1 Wettig p. 47