Step 1 : Introduction to the question "World War II started when Germany invaded which country?"
...World War II began on September 1, 1939, when Nazi Germany invaded Poland in a swift, coordinated assault known as Blitzkrieg, or “lightning war.” The attack prompted Britain and France to declare war on Germany, marking the official start of the global conflict. While Germany had earlier annexed Austria and taken part of Czechoslovakia without triggering a world war, the brutal invasion of Poland was the decisive breaking point that set off a cascading chain of alliances and military responses that ultimately engulfed the entire world.
