The week before the outbreak of war
Adolf Hitler is determined to resolve the open Danzig question, the problem of the transport of East Prussia to the Reich and the protection of minorities for the Germans in Poland before the winter on the negotiation path or, if this is not possible, with a war. The Generality has warned several times that a war with Poland would also lead to war with England, with France, and with a long-term relationship with the USA, and that a two-fronted war could not be won. Hitler planned to strike Poland 29. August, but the same day the Polish - British alliance has been declared, that postponed the attack by two days.
(src wikipedia)
The Second World War began on September 1, 1939, with the attack of the German army on Poland. Hitler was expecting that Great Britain and France will abandon their allies and he was technically right. Great Britain and France declared war of Poland, but no soldier and no weapon supply went to support struggling Poles.
The Western powers are determined to militarily oppose the threat to freedom and democracy in Europe after the defeat of Czechoslovakia and the annexation of the Memel area have shown that Hitler will not stick to the agreements reached at the Munich Conference in 1938.
(French newspaper headline: Why die for Danzig?)
On 17. September the USSR attacks Poland, meaning country without allies is deemed to capitulate. Just in October 1939 the "Fall Weiss" (White Plan, codename for the Nazi German aggression of Poland) is completed.