ORDER OF BATTLE // September 17, 1939
Soviet invasion of Poland
Estimated force strength by side, with confidence labels per surviving record.
Forces engaged
2 sides catalogued · combined 620,000–820,000 estimated
Poland
20,000
Medium-confidence figure
Soviet Union
600,000–800,000
Medium-confidence figure
Battle context
The Soviet invasion of Poland on 17 September 1939 completed the strategic encirclement of the Second Polish Republic, which was already engaged against Nazi Germany's invasion from the west sixteen days earlier. Launched without a formal declaration of war, the Soviet operation was directly tied to the secret protocol of the Molotov–Ribbentrop Pact signed on 23 August 1939, which had divided Poland into predetermined spheres of influence between the two powers. Facing a combined Soviet force of 600,000–800,000 troops against a Polish force of approximately 20,000 in the east, organized Polish resistance collapsed within 20 days. By 6 October 1939, the entire territory of the Second Polish Republic had been partitioned and annexed between Nazi Germany and the Soviet Union — an outcome historians have characterized as the Fourth Partition of Poland. The German-Soviet co-belligerence that produced this result demonstrated the operational consequences of the Pact and eliminated Poland as an independent state for the duration of the war, fundamentally altering the strategic map of Eastern Europe at the outset of the conflict.
‹ Full battle dossier