This article from the Encyclopedia Britannica gives you an introduction to World War 2. Make sure that you also look at the primary sources and images and videos provided.
This offering from the Smithsonian includes information on various aspects of WW2: Mobilizing Children, Changing Gender Roles and the Battle of the Bulge. Unfortunately, you may be unable to view the videos.
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Author: United States Strategic Bombing Survey
Publisher: United States Government Printing Office
Place of publication: Washington
Date: 1946