Horst Steinert was born in Berlin in 1917. He came from a working class family. Early on he was active in communist organizations. He broke off his training as a saddler and carpenter and worked as a messenger for the Deutsche Tachometerwerke. At the same time he learned the art of writing at the Kunstgewerbeschule Berlin. After 1933 he led a resistance group of the German Communist Youth Association (KJVD) and was involved in the production of illegal leaflets. In July 1935 he was arrested and sentenced to three and a half years in prison for preparation for high treason.
Through a friend of his father's, Horst Steinert was given a job at the company Willy Haupt in Berlin-Neukölln, which was responsible for pest control in numerous forced labor camps. The company's employees had set up secret contact groups in the camps. They smuggled secret cash, medicines and food into the containers with disinfectants.
After 1945, Steinert and his wife Irmgard, née Dombrowski, went into business for themselves as pest controllers in the GDR. Due to years of contact with poisons, both suffered damage to their health. Because of debts Horst was deprived of his status as a victim of fascism. Also the permission for an independent activity was withdrawn from him. The Steinerts lived in poor conditions. After 1989, Steinert received compensation. He died in 2000.