France and the United Kingdom did not immediately launch attacks after declaring war in 1939. France fell to Germany's blitzkrieg in 1940, and the Wannsee Conference in 1942 planned the mass killing of European Jews.
After declaring war on September 3, 1939, France and the United Kingdom did not immediately launch attacks against Germany. They declared war but there was a period known as the 'Phony War' where very little happened. France fell to Germany's blitzkrieg tactics in 1940. The Wannsee Conference in 1942 was indeed a meeting where Nazi officials planned the mass killing of European Jews.
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