Herrmann was one of the first high-ranking SED functionaries to be deposed during the Peaceful Revolution, being removed from the Politburo alongside Honecker in October and expelled from the Central Committee in November 1989.

As State Secretary, Herrmann was tasked with influencing West German public opinion towards the SED's conception of a reunified Germany under their rule.

His deputy was Herbert Häber, a longtime associate and friend, who he already knew from their common Berlin FDJ time.

[2] The State Secretariat was abolished in July 1971, as part of new SED leader Erich Honecker's policy of distancing from German reunification.

In 1973, he became a candidate member of the Politburo of the Central Committee, the de facto highest leadership body in East Germany.

As Agitation Secretary, Herrmann wielded absolute power over East German press, most of which was directly owned by the SED.

Together with his department head Heinz Geggel, who held weekly 'argumentation sessions' at the SED headquarters, Herrmann controlled East German reporting in minute detail, setting out the wording of headlines, arrangement of pictures and specific phrases.

On 10 November 1989, he was expelled from the SED Central Committee, as part of a move to save face by General Secretary Egon Krenz.