1939On September 1, 1939, Germany invaded Poland in the free city of Danzig, marking the beginning of World War II. The invasion was part of Hitler's plan to expand Germany's territory and establish dominance over Europe. Despite efforts to negotiate a peaceful resolution, the invasion triggered a swift response from Britain and France, which declared war on Germany two days later. The invasion of Poland led to one of the deadliest conflicts in human history, with millions of lives lost before the war ended in 1945.