He co-founded the Spartacus League and the KPD, rising to become chairman of the latter organization following the imprisonment of Ernst Thälmann and John Schehr by the Nazis.

On 16 January 1919 Pieck, along with Rosa Luxemburg and Karl Liebknecht, was arrested in Berlin's Wilmersdorf district and taken to the Eden Hotel.

[8] According to Waldemar Pabst (the officer who gave the order to kill Liebknecht and Luxemburg), Pieck did not actually escape, but was released in return for providing details about the military plans and hiding places of other KPD members.

[11] On 4 March 1933, one day before the Reichstag election, Pieck's family left their Steglitz apartment and moved into a cook's room.

In 1943 Pieck was among the founders of the National Committee for a Free Germany, an anti-Nazi organisation created by the Soviets aimed at Germans.

[12] A year later, he helped engineer the merger of the eastern branches of the KPD and SPD into the Socialist Unity Party (SED).

[13] Nominally, for the GDR's first year, Pieck was the number-two man in the government behind Grotewohl, who became the new country's first prime minister.

In the East German political hierarchy, the prime minister was the top state official, while the president nominally ranked second.

He nominally held the second highest state post in the GDR (behind Prime Minister Grotewohl) and served as SED co-chairman for the first four years of the party's existence.

A detailed medical report composed before the second stroke mentioned "mild paralysis on the right, a slight drooping of the corner of the mouth, breathing wheezing or snoring, slowed down pulse, tone of the limb musculature lowered ...".

He was honoured with a state funeral, cremated and buried at the Memorial to the Socialists (German: Gedenkstätte der Sozialisten) in the Friedrichsfelde Central Cemetery, Berlin.

He was married to Christine Häfker,[2] a garments worker whom he met in a large dance hall in Bremen.

At first, her parents did not want her to go out with a "red", but once she was pregnant, she was allowed to marry Wilhelm on 28 May 1898, on the condition that a traditional wedding in a church would still take place.

The Piecks' daughter, Elly Winter (1898–1987), held various posts in the SED and East German government.