September 1, 1939 – September 2, 1945
The major causes of World War II were numerous. They include the impact of the Treaty of Versailles following WWI, the worldwide economic depression, failure of appeasement, the rise of militarism in Germany and Japan, and the failure of the League of Nations. Hitler's invasion of Poland in September 1939 drove Great Britain and France to declare war on Germany, marking the beginning of World War II. Over the next six years, the conflict would take more lives and destroy more land and property around the globe than any previous war. Many Americans volunteered to defend the nation from enemy bombing or invasion. They trained in first aid, aircraft spotting, bomb removal, and fire fighting. Air raid wardens led practice drills, including blackouts. By mid-1942 over 10 million Americans were civil defense volunteers.
