World War II in Europe from 1939 to 1941 saw rapid German expansion and the fall of several nations. Key events included the invasion of Poland, the Battle of France, and Operation Barbarossa against the Soviet Union. The Axis powers, led by Germany, faced off against the Allies, including Britain and France. The period was marked by blitzkrieg tactics, the Battle of Britain, and the formation of crucial alliances that shaped the conflict's trajectory.