The Ministry for State Security commonly known as the Stasi (abbreviation German: Staatssicherheit, literally State Security), also State Security Service (German Staatssicherheitsdienst, SSD), was the official state security service of the German Democratic Republic (GDR) (Deutsche Demokratische Republik, DDR), colloquially known as East Germany. It has been described as one of the most effective and repressive intelligence and secret police agencies to have ever existed. Headquartered in East Berlin, with an extensive complex in Berlin-Lichtenberg and several smaller facilities throughout the city. The Stasi motto was "Schild und Schwert der Partei" (Shield and Sword of the Party), referring to the ruling Socialist Unity Party of Germany. Erich Mielke was its longest-serving chief, in power for thirty-two of the GDR's forty years of existence.

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