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.
<h2><u><em>Hitler had long planned an invasion of Poland, a nation to which Great Britain and France had guaranteed military support if it was attacked by Germany. ... On September 1, 1939, Hitler invaded Poland from the west; two days later, France and Britain declared war on Germany, beginning World War II.</em></u></h2>
