World War II ranged from 1939 through 1945 and it involved every major world power. On one side were the Allies, including Great Britain, the United States, France and the Soviet Union. On the other side the Axis powers included Germany, Japan and Italy. This conflict resulted from the rise of totalitarian, militaristic regimes in Germany, Japan and Italy after World War I. Partly responsible were the humiliating peace treaties forced on Germany after World War I. The Great Depression of the 1930's created world wide economic disorder and thus contributed to the war. During the 1930's Japan was very aggressive in Asia and Italy, lead by Mussolini was invading Ethiopia. French and British appeasement of Hitler's Nazi regime in Germany culminated in the Munich Pact of 1938. This sacrificed much of Czechoslovakia to Germany. France and Britain began to rearm and to offer guarantees to other potential victims of the Nazi aggression. .
In August of 1939 Germany and the Soviet Union, previously bitter enemies, concluded a non-aggression pact, thus freeing Hitler to invade Poland on September 1, 1939. France and Britain immediately declared war on Germany officially beginning World War II. Germany won a quick victory in Poland and went on to occupy Norway and Denmark in 1940. In May they over ran the Low Countries and broke into France and swept into the English Channel. On June 22, 1940 France surrendered. However a free French force continued to fight. Britain under Prime Minister Winston Churchill was left to fight alone. .
The Battle of Britain lasted from August to October 1940. Germany's attempt to bomb Britain into submission was the only German failure of the wars early years. Axis's land operations continued in North Africa and in the Balkans, where Greece and Yugoslavia were occupied. On June 22, 1941 Germany invaded the Soviet Union bringing that nation under Premier Joseph Stalin into the war.