12. The invasion of Poland by _______ led to France and Britain declaring war on the aggressor nation. This is commonly considered the official start of World War II.
The German invasion of Poland was a military action of Nazi Germany aimed at annexing the Polish territory. The technical operation, known as "White Case" (in German, Fall Weiss), began on September 1, 1939 and the last units of the Polish army surrendered on October 6 of that same year. It was the trigger of the Second World War in Europe and ended with the Second Polish Republic.
