Eichhorn was born in Röhrsdorf (now part of Chemnitz) in the Kingdom of Saxony in October 1863 and became apprenticed as a glass worker in 1878, becoming active in the Social Democratic Party of Germany (SPD).

[1] He became a full-time official in 1893 and was the head of its press office from 1908–17, when he left with others to form the USPD where he played a similar role.

[3] On 9 November 1918 he led the occupation of police headquarters in Berlin, the infantry guarding the building surrendering their weapons without a struggle.

"[8] The attempt to remove Eichhorn had been preceded by slander in Vorwärts accusing him of having received Russian gold, possessing stolen foodstuffs and illegally bought arms.

Earlier that day his supporters had occupied several buildings, including the Vorwärts office, in the precursor to the Spartacist uprising.