What german institution did german chancellor otto von bismarck (1815-1898) attack in 1878, after the failure of his kulturkampf?

The answer is SDP or the Social Democratic Party. The SDP was led by Martin Schulz, it became one of the major political parties in the country of Germany together with the CDU or the Christian Democratic Union.

The said party was a member of Socialist International and Party of European Socialists and also the founder of Progressive Alliance.