Britain and France had signed a guarantee promising military assistance to Poland — and then did nothing. Prime Ministers Neville Chamberlain and Édouard Daladier met, adopted a "long war strategy," and effectively cast Poland to the winds. Neither country was militarily nor mentally prepared to act when it mattered most.
When Germany crossed the Polish border on September 1, 1939 — with 1.5 million men, 1,300 planes, and 2,750 tanks — the world expected Britain and France to respond with force. They had promised exactly that. The guarantee to Poland was unambiguous on paper.
In practice, Chamberlain and Daladier convened a supreme war council and chose delay over action. Their calculation was strategic, not cowardly in their own minds: they believed the Allies held superior long-term resources, and that time would ultimately work in their favor.
The result was a public statement of "wholehearted support" for Poland paired with zero meaningful military intervention. Warsaw was left to fight alone against the Wehrmacht and the Luftwaffe. Hear the full episode on Listenly to understand how this strategic paralysis shaped the war's opening months.
The Allied doctrine formally adopted in September 1939 rested on a single assumption: that the British Empire and French Republic could outlast Germany through economic and industrial attrition. Churchill's war cabinet later framed it as preparing for a conflict of at least three years.
It was a theory built for the future — and a death sentence for Poland in the present. While Chamberlain and Daladier planned for a prolonged contest of resources, Polish cities were being demolished and Polish civilians were dying under German bombs and occupation.
The strategic logic was real. The human cost of that logic, for Poland, was catastrophic and immediate.
"Poland has been overrun by two of the great powers which held us in bondage for 150 years, but were unable to quench the spirit of the Polish nation. The heroic defence of Warsaw shows that the soul of Poland is indestructible."
— Spoken in the episode, reflecting the defiant Polish perspective as both Germany and the Soviet Union — following the Molotov-Ribbentrop Pact — moved to divide and occupy the country.
Göring ordered the largest air raid ever seen to break Warsaw's resistance, dropping thousands of pounds of high-explosive and incendiary bombs over the city. The raids destroyed 20% of Warsaw and killed or injured approximately 18,000 people.
The Einsatzgruppen were mobile death squads — a special wing of the SS specifically set up to go into towns, villages, and other areas of Poland to kill targeted populations during the invasion.
In August 1939, just one week before Germany invaded Poland, Stalin shocked the world by signing a non-aggression pact with Hitler. Beyond the public pledge, secret provisions divided Eastern Europe — including Poland — into German and Soviet spheres of influence.
This answer comes directly from World War II with Tom Hanks, Episode 1: The Beginning.
Listen to the episode on Listenly