The 'stab-in-the-back' legend (Dolchstosslegende) became popular among right wing nationalists in Weimar Germany after the end of World War One. The Weimar politicians were referred to as “traitors” who had been responsible for the 'stab-in-the-back' of the German military. Little could persuade those who expounded the 'stab-in-the-back' legend that there was little substance in their arguments and even a post-war Reichstag commission stated that the 'stab-in-the-back' legend had little substance in it but that some people were responsible for failing to fully support the military.
In the spring of 1918, the German army launched its Spring Offensive. This was spectacularly successful to start with. German storm troopers redefined the way infantry fought on the Western Front. However, it failed probably because it was initially too successful. The attack swept aside all Allied forces in front of it and nearly reached the very important rail city of Amiens. However, by advancing so far and so quickly, the Germans had stretched their supply lines to the very limit and they could not supply those at the very front of the attack. As a result the attacked petered out and a withdrawal was inevitable. The Spring Offensive was the last success of the German army in the western sector of the war and after 'Black Monday' the withdrawal became chaotic and defeat was inevitable. The Germans simply could not match the combined might of the Americans, British/Commonwealth and French troops.
However, right wing extremists refused to accept that there was primarily a military explanation to the defeat. However, the right wing groups that existed in Weimar Germany had made up their minds and their explanation was simple: Germany had been betrayed by Jewish-Bolshevik traitors who had worked to ensure Germany's defeat - the 'stab-in-the-back' legend.
The term 'stab-in-the-back' was first used on December 1st 1918 in a report from England published in the 'Neue Züricher Zeitung':
“As far as the German army is concerned the general view is summarised in these words: It was stab-in-the-back by the civilian population.”
A formal Reichstag commission of enquiry was held by the Weimar government. It was chaired by Albrecht Philip and the final report was written by General Hermann von Kuhl. The report mildly criticised the 'stab-in-the-back' legend but it did not reject it out of hand.
“The expression 'stab-in-the-back' in the oft-used sense, as if the country had attacked the victorious army in the rear and as if the war had been lost for this reason alone, is not accurate. We succumbed for many reasons.”
The report blamed “a pacifistic, international, anti-military and revolutionary undermining of the army” for the defeat and that this movement “originated at home but the blame does not attach to the entire population, which in four and a half years of war endured superhuman sufferings.”
The report stated that the blame for the situation that the army found itself in should be attached “only to the agitators and corruptors of the people and of the army who for political reasons strove to poison the bravely-fighting forces. One should therefore speak not of a 'stab-in-the-back' but of a poisoning of the army.”
The report placed a great deal of blame on the German military collapse on the German Revolution. The impact of the revolution was “sudden” and “devastating”.
“It (the revolution) literally attacked the army from the rear, disorganised the lines of communication, preventing the forwarding of supplies and destroyed all order and discipline as if at a blow. It made all further fighting impossible.”
The commission's chairman added a paragraph that stated:
“In view of the many interpretations of the expression 'stab-in-the-back', it is better not to use this term for the influences which, coming from home, weakened the army's will to fight. Von Kuhl declares quite correctly: “We succumbed for many reasons”. The expression 'stab-in-the-back' is absolutely correct as a criticism of the revolution as a single event, but it can be applied only with limitations to the motive powers of the development which prepared the ground for the German Revolution.”