September 1, 1939, Germany invades Poland.
September 3, Britain and France declare war. Churchill speaks in the House of Commons:
We must not underrate the gravity of the task which lies before us or the severity of the ordeal, to which we shall not be found unequal. We must expect many disappointments, and many unpleasant surprises …
This is not a question of fighting for Danzig or fighting for Poland. We are fighting to save the whole world from the pestilence of Nazi tyranny and in defense of all that is most sacred to man. This is no war of domination or imperial aggrandizement or material gain; no war to shut any country out of its sunlight and means of progress. It is a war, viewed in its inherent quality, to establish, on impregnable rocks, the rights of the individual, and it is a war to establish and revive the stature of man.
September 27, Warsaw falls.
The Germans immediately begin planning their assault on the West.
The seeds had long been planted and the harvest of appeasement was being gathered in.