On 1 September 1939, Germany invaded western Poland under the pretext of having been denied claims to the Free City of Danzig and the right to extraterritorial roads across the Polish Corridor, which Germany had ceded under the Versailles Treaty.
In 1939 Kennedy toured Europe, the Soviet Union, the Balkans, and the Middle East in preparation for his Harvard senior honors thesis. He then went to Czechoslovakia and Germany before returning to London on September 1, 1939, the day that Germany invaded Polandto mark the beginning of World War II.
When Germany invaded Poland on 1 September 1939, triggering a declaration of war from France and the UK, it gained control of an additional two million Jews, reduced to around 1.7 – 1.8 million in the German zone when the Soviet Union invaded from the east on 17 September.
Despite the outbreak of World War II on 1 September 1939, the widowed Stravinsky sailed (alone) for the United States at the end of the month, arriving in New York City and thence to Cambridge, Massachusetts, to fulfill his engagement at Harvard.
On 2 September 1939 (the day after the start of the war), Goebbels and the Council of Ministers proclaimed it illegal to listen to foreign radio stations. Disseminating news from foreign broadcasts could result in the death penalty.
On 3 September 1939, the day Britain declared war on Germany, Chamberlain reappointed Churchill as First Lord of the Admiralty and he joined Chamberlain's war cabinet. Churchill later claimed that the Board of the Admiralty sent a signal to the Fleet: "Winston is back".
The United Kingdom responded with an ultimatum to Germany to cease military operations, and on 3 September, after the ultimatum was ignored, France and Britain, along with their empires, declared war on Germany. The alliance provided no direct military support to Poland, outside of a cautious French probe into the Saarland.
The Polish counter offensive to the west halted the German advance for several days, but it was outflanked and encircled by the Wehrmacht. The Battle of the Bzura fought between 9 and 19 September 1939, It began as a Polish counter-offensive, but ended with German victory, German forces took all of western Poland.
On the outbreak of the Second World War in September 1939, the Duke and Duchess were brought back to Britain by Louis Mountbatten on board HMS Kelly, and Edward, although an honorary field marshal, was made a major-general attached to the British Military Mission in France.
In November 1939, the United States was taking measures to assist China and the Western Allies, and amended the Neutrality Act to allow "cash and carry" purchases by the Allies. Cash and carry was a policy by US President Franklin Delano Roosevelt announced at a joint session of the United States Congress on September 21, 1939, subsequent to the outbreak of war in Europe. It replaced the Neutrality Acts of 1937, by which belligerents could purchase only nonmilitary goods from the United States as long as the recipients paid immediately in cash and assumed all risk in transportation using their own ships.
According to a letter dated 21 September 1939 from SS-Obergruppenführer Reinhard Heydrich, head of the Reichssicherheitshauptamt (RSHA or Reich Security Head Office), to the Einsatzgruppen, each ghetto had to be run by a Judenrat, or "Jewish Council of Elders", to consist of 24 male Jews with local influence.
In September 1939, Britain entered the Second World War. Lord Hailsham suggested that Princesses Elizabeth and Margaret should be evacuated to Canada to avoid the frequent aerial bombing. This was rejected by their mother. The princesses stayed at Balmoral Castle, Scotland, until Christmas.
The Soviet Union forced the Baltic countries—Estonia, Latvia and Lithuania, the states that were in the Soviet "sphere of influence" under the Molotov-Ribbentrop pact—to sign "mutual assistance pacts" that stipulated stationing Soviet troops in these countries.
On 29 September 1939, soon after the start of the Second World War, Rear Admiral John Godfrey, the Director of Naval Intelligence, circulated the Trout memo, a paper that compared the deception of an enemy in wartime to fly fishing.