The Treaty of Versailles in the mind of the Germans stabbed them in the back, especially the guilt clause that made them take blame for the First World War. Hitler capaitalized on these sentiments and used them to rally the German people.
Primary sources are the first hand evidence left behind by participants or observers at the time of events. Primary sources originate in the time period that historians are studying. They vary a great deal.
A primary source is an original object or document-- the raw material or first-hand information, source material that is closest to what is being studied. Primary sources vary by discipline and can include historical and legal documents, eye witness accounts, results of an experiment, statistical data, pieces of creative writing, and art objects.