What prompted Great Britain and France to declare war on Germany?*

A. Soviet invasion of Finland

B. German invasion of Poland

C. German invasion of Czechoslovakia

D. Soviet invasion of Poland

On September 17, 1939, the Soviet Union invaded eastern Poland, sealing Poland's fate ... After Poland's defeat in early October 1939, Nazi Germany and the Soviet Union divided the country in accordance with a secret clause in the German-Soviet Non-Aggression Pact.

Britain and France declare war on Germany. On September 3, 1939, in response to Hitler's invasion of Poland, Britain and France, both allies of the overrun nation declare war on Germany