You can read about the famous “stab in the back” on Wikipedia at
The following quote is from Wikipedia:
The stab-in-the-back myth (German: Dolchstoßlegende, pronounced [ˈdɔlçʃtoːsleˌɡɛndə] ( listen)) was the notion, widely believed in right-wing circles in Germany after 1918, that the German Army did not lose World War I but was instead betrayed by the civilians on the home front, especially the republicans who overthrew the monarchy in the German Revolution of 1918–19. Advocates denounced the German government leaders who signed the Armistice on November 11, 1918, as the “November Criminals” (German: Novemberverbrecher).
When the Nazis came to power in 1933, they made the legend an integral part of their official history of the 1920s, portraying the Weimar Republic as the work of the “November criminals” who used the stab in the back to seize power while betraying the nation.
The Nazi propaganda depicted Weimar as “a morass of corruption, degeneracy, national humiliation, ruthless persecution of the honest ‘national opposition’—fourteen years of rule by Jews, Marxists, and ‘cultural Bolsheviks’, who had at last been swept away by the National Socialist movement under Adolf Hitler and the victory of the ‘national revolution’ of 1933″.
Scholars inside and outside Germany unanimously reject the notion, pointing out the German army was out of reserves and was being overwhelmed in late 1918. To many Germans, the expression “stab in the back” was evocative of Richard Wagner‘s 1876 opera Götterdämmerung, in which Hagen murders his enemy Siegfried with a spear in his back.