In 1929, Thälmann and Stalin agreed upon an ultra-left course against the SPD, concluding that the Social Democrats represented a form of “social fascism”. This disastrous line would eventually prove fatal for both the Social Democrats and the Communists.
The theory of social fascism dictated that Nazis and Social Democrats were essentially two sides of the same coin. The primary enemy of the Communists was supposedly the Social Democrats, who protected capitalism from a workers’ revolution by deceiving the class with pseudo-socialist rhetoric. The worst of them all were the left wing Social Democrats, whose rhetoric was particularly deceptive. According to the theory, it was impossible to fight side by side with the SPD against the Nazis under such conditions. Indeed, the KPD declared that defeating the social fascists was the “prerequisite to smashing fascism”. By 1932 the KPD began engaging in isolated attempts to initiate broader anti-fascist fronts, most importantly the Antifascischistsche Aktion, but these were formulated as “united fronts from below”—ie without the leadership of the SPD. Turning the logic of the united front on its head, SPD supporters were expected to give up their party allegiance before joining, as opposed to the united front being a first practical step towards the Communist Party. Throughout this period the leaderships of both the SPD and the KPD never came to a formal agreement regarding the fight against Nazism.
Another fatal consequence of the KPD’s ultra-leftism was that the term “fascism” was used irresponsibly to describe any and all opponents to the right of the party. The SPD-led government that ruled Germany until 1930 was considered “social fascist”. When Brüning formed a new right-wing government by decree without a parliamentary majority in 1930, the KPD declared that fascism had taken power. This went hand in hand with a deadly underestimation of the Nazi danger. Thus Thälmann could declare in 1932: “Nothing could be more fatal for us than to opportunistically overestimate the danger posed by Hitler-fascism”. The KPD’s seeming inability to distinguish between democratic, authoritarian and fascist expressions of capitalist rule proved to be its undoing. An organisation that continually vilified bourgeois democratic governments as fascist was unable to understand the true meaning of Hitler’s ascension to power on 30 January 1933, the day the KPD infamously (and ominously) declared: “After Hitler, we will take over!”
https://isj.org.uk/divided-they-fell-the-german-left-and-the-rise-of-hitler/
The Communists were the only organization of the working class that organized extra-parliamentary resistance to the Nazis while opposing the government’s austerity drive, but they too failed. Their failure was due largely to an inability to develop a clear analysis of fascism and comprehend the threat it posed.
The Central Committee overused the phrase “fascism” to the point of meaninglessness. As far as they were concerned, the German state had become fascist in 1930 when Hindenburg’s presidential cabinet took over. Indeed, the KPD leadership considered all other parliamentary parties to be variants of fascism, telling its members that “fighting fascism means fighting the SPD just as much as it means fighting Hitler and the parties of Brüning.”
The KPD took its position from Moscow, basing itself on the theory of “social fascism” that fascism and Social Democracy were not opposed but in fact functioned like “twin brothers,” as Stalin had once argued. In the context of deep capitalist crisis, it was Social Democracy — holding back the workers from fighting capitalism — that constituted the “main enemy.”
Following this line, the leadership rejected all cooperation with the SPD, even when it came to fighting the Nazis: “The social fascists know that for us there can be no collaboration with them. With respect to the party of the Panzerkreuzer, the police-socialists and those paving the way for fascism, for us there can only be a fight to the death.”
Many Communists endorsed these sorts of radical-sounding phrases, as the KPD was increasingly a party of the unemployed. Communist workplace organization had almost ceased to exist. By the fall of 1932, only 11 percent of KPD members were waged laborers.
Thus, most Communists no longer knew Social Democrats as work colleagues, but only as supporters of the lesser-evil strategy and events like “Bloody May” on May 1, 1929, when police under the command of Social Democrat Karl Friedrich Zörgiebel violently suppressed a KPD-led demonstration.
Accentuating the blockade was the SPD leadership’s outright refusal to collaborate with the Communists. The SPD at the time was consumed by an anti-Communist fervor, often equating Communism with Nazism. Party Chairman Otto Wels declared at the Leipzig party convention in 1931 that “Bolshevism and fascism are brothers. They are both founded on violence and dictatorship, regardless of how socialist or radical they may appear.”
Rather than offering the majority of the population a political alternative, the KPD’s policy of directing most of its ire against the SPD drove it into the arms of the Right, at least for a little while. The most notorious example of this occurred in 1931, when the KPD supported a popular referendum against the Prussian SPD government initiated by Nazis and other nationalist forces.
https://www.jacobinmag.com/2015/11/nuremberg-trials-hitler-goebbels-himmler-german-communist-social-democrats
Sound familiar, core?