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.
The secondary source is the evidence of someone who was not present at the time of occurrence of the event e.g., books written by historians. The secondary source is also of great historical importance to the historians. Although secondary source is itself dependent on primary sources. A primary source may contain secondary information e.g., news papers are usually considered primary sources but the information provided by news paper is not all based on primary sources.