World War II Timeline: September 1939

A dated guide to 6 documented events in September 1939, with links to individual historical records.

Dated historical records

Entries below follow the dates recorded in the WWII CHRONOS archive. Each linked title opens the original historical entry, including its source reference.

1. 1939-09-01 — First Full-Scale Polyethylene Plant Begins Operation — Polyethylene moves from laboratory material to industrial production.
2. 1939-09-01 — German Invasion of Poland — The beginning of the Second World War in Europe; Germany attacks from the west.
3. 1939-09-03 — Britain and France Declare War — The two states enter the war against Germany following the invasion of Poland.
4. 1939-09-14 — First Flight of the Sikorsky VS-300 Helicopter — A key prototype for the modern single-main-rotor helicopter configuration.
5. 1939-09-17 — Soviet Invasion of Poland — The Red Army enters eastern Poland in accordance with the Soviet-German division of spheres of influence.
6. 1939-09-28 — Surrender of Warsaw — After Germany's attack on Poland, Warsaw came under siege. The city's defenders and civilian population endured heavy artillery fire and bombing.

For wider context, explore the interactive historical timeline and compare events across theaters.