For example many CPSU members were formally members of the social democratic party, almost all Eastern Bloc communist parties were mergers of the preexisting communist parties with social democratic parties, and the Korean Social Democratic Party is one of the few opposition parties in the DPRK
Social Democracy is what all the socialists called themselves. Then in WWI the SocDems betrayed the international proletariat and supported their own states’ armies, so Lenin switched to calling his people communists like Marx intended. Also the German SPD used to be one of the more progressive parties, but they were revisionist and the principled communists split and led a revolution, but were defeated by the SPD making way for Hitler.
Why did Socialist Unity Party of Germany merge with post-WW2 SPD then?
It was not voluntary.
Please explain
The man in your pfp used the power of violence to crush fascism and try to fold the sucdems into actual socialists. Didn’t work, sadly.
Idk, I’m not an expert, just giving some basic explanation for the relation of Social Democracy and Communism.