Poland
1939: The September Campaign
September – October 1939 · 8 battles
On 1 September 1939 Germany attacked Poland from three sides, and on 17 September the Red Army struck from the east. The Polish Army, stretched along a long frontier and denied the help its allies had promised, fought many fierce battles, from Westerplatte and Mokra to the Bzura, the defence of Warsaw and Kock. The campaign lasted more than five weeks and ended in the fourth partition of Poland, between the Third Reich and the USSR, but the Polish state did not capitulate: the government went into exile, and thousands of soldiers made their way to the West to fight on.
- 1–3 September 1939Battle of MławaFrom 1 to 3 September 1939 Army Modlin held the Mława fortifications against the German Third Army. The Germans broke through at Rzęgnowo and forced a retreat.
- 1 September – 6 October 1939Key battleInvasion of PolandFrom 1 September to 6 October 1939 Poland fought Nazi Germany, Slovakia and, from 17 September, the Soviet Union. The campaign ended in partition.
- 1 September – 2 October 1939Battle of HelFrom 1 September to 2 October 1939 some 3,000 soldiers and sailors held the Hel Peninsula, the last Polish centre of resistance on the Baltic.
- 1–7 September 1939Battle of WesterplatteFrom 1 to 7 September 1939 some 200 Polish soldiers held the Westerplatte depot against a battleship, naval infantry, Danzig police and Stukas.
- 8–28 September 1939Siege of Warsaw (1939)Warsaw held out against the Wehrmacht and Luftwaffe from 8 to 28 September 1939, surrendering after mass air raids, without water, power or hope of relief.
- 9–22 September 1939Battle of the BzuraFrom 9 to 22 September 1939 Kutrzeba's Poznań and Pomorze Armies struck the flank of the German 8th Army. After early success they were encircled and crushed.
- 17 September – 6 October 1939Soviet invasion of PolandFrom 17 September 1939 the Red Army occupied eastern Poland, resisted by the KOP, Grodno, Lwów and Orlik-Rückemann's group. Fighting went on into October.
- 2–5 October 1939Battle of KockOn 2–5 October 1939 Kleeberg’s Operational Group Polesie fought the German XIV Corps. It won its last battle but, out of ammunition, surrendered on 6 October.