Key Facts
- Duration
- 1 September – 6 October 1939 (35 days)
- Attacking powers
- Nazi Germany, Soviet Union, Slovak Republic
- Soviet invasion date
- 17 September 1939
- Trigger event
- Gleiwitz incident; Molotov–Ribbentrop Pact signed 23 August 1939
- Allied response
- UK and France declared war on Germany on 3 September 1939
- Polish formal surrender
- Poland never formally surrendered
Strategic Narrative Overview
German forces advanced rapidly, pushing Polish defenders eastward. After Poland's defeat at the Battle of the Bzura in mid-September, Germany held a decisive advantage. On 17 September, Soviet forces invaded eastern Poland, collapsing the Polish plan to hold a Romanian Bridgehead. Facing two fronts simultaneously, the Polish government ordered evacuation to Romania. The final Polish resistance ended at the Battle of Kock on 6 October 1939.
01 / The Origins
Tensions escalated through the Danzig crisis as Nazi Germany demanded territorial concessions from Poland. One week after signing the Molotov–Ribbentrop Pact—which secretly divided Eastern Europe into German and Soviet spheres of influence—Germany staged the Gleiwitz incident as a pretext. On 1 September 1939, German and Slovak forces invaded Poland from the north, south, and west, triggering British and French declarations of war on Germany two days later.
03 / The Outcome
Germany and the Soviet Union divided all of Poland under the German–Soviet Frontier Treaty. Germany annexed western Poland and Danzig, placing remaining territory under a General Government; the USSR incorporated eastern regions into Soviet republics and began Sovietization. Poland never formally surrendered. A Polish government-in-exile and underground resistance continued operations, while escaped military personnel formed the Polish Armed Forces in the West.
Belligerents & Mobilization Analysis
Side A
3 belligerents
Adolf Hitler, Joseph Stalin.
Side B
1 belligerent
Edward Rydz-Śmigły.
Kinetic Engagement Axis
Scroll horizontally to view full axis. Events plotted relatively.