The Eastern SPD and the KPD merged to form the SED [Sozialistische Einheitspartei Deutschlands or Socialist Unity Party] at the Unification Party Congress in Berlin's Admiralpalast on April 21-22, 1946. Scholarly disputes about the nature of the SED's founding – and divergent interpretations of it as a "voluntary merger" or a "forced unification" – are almost as old as the party itself. Newer research utilizing sources that have become available since 1990 clearly demonstrates that the pressure and intimidation tactics of German and Soviet Communists played an essential role in the founding of the SED. Here, Wilhelm Pieck (KPD, left) and Otto Grotewohl (Eastern SPD) shake hands. Seated on the right: Walter Ulbricht.