Germany's two separate labor parties, both threatened by Bismarck's policies, unite to form the 
Socialist Workers' Party of Germany (German: Sozialistische Arbeiterpartei Deutschlands, SAPD) at a congress in Gotha from May 22-27, where fifty-five SDAP delegates have joined seventy-three ADAV delegates.

The resultant Gotha Program is a mixture of socialist and liberal capitalist ideas.

Though it largely satisfies the conventioneers, the new policies will be denounced by Karl Marx himself in the scathing essay Critique of the Gotha Program (1875).

Marx had sent programmatic suggestions to the Gotha Congress, but the newly united socialist party adopts an essentially Lassallean policy.

Wilhelm Liebknecht becomes one of the leaders of the SDAP and the leading publisher of the party organ, Der Volksstaat ("the People's State"), the first issue of which is published on October 1 in Leipzig, under the editorship of Liebknecht and Wilhelm Hasenclever (until 1878).

It will henceforth be published three times weekly, and will be the official newspaper of the SPD until the 1990s.

Wilhelm II of Germany opposes Otto von Bismarck's attempt to renew the law outlawing the Social Democratic Party.

Wilhelm forces Bismarck to resign as Chancellor in 1890.

The new emperor allows the Reinsurance Treaty between Germany, Austria-Hungary and Russia to fall apart.

The German Social Democratic party upholds revolutionary Marxism through the Erfurt program, much of it authored by Karl Kautsky.