On September 1, 1939, Nazi Germany invaded Poland, marking the beginning of World War II. The attack was brutal, with German forces using blitzkrieg tactics to quickly overwhelm Polish defenses. This invasion prompted Britain and France to declare war on Germany, formally beginning the conflict that would involve most of the world. The invasion led to the division of Poland between Nazi Germany and the Soviet Union. Millions of Polish civilians would suffer, many falling victim to the wars atrocities, including the Holocaust.