The Ministry for State Security (MfS) of the German Democratic Republic (GDR), founded in 1950, saw itself as the "shield and sword of the party." In practice, this meant espionage, repression, and disruption. Its main target was its own population. The Stasi, as the MfS was commonly known, was the most important early warning system and repressive apparatus of the Socialist Unity Party of Germany (SED).

Nevertheless, the Stasi could not prevent the fall of the Berlin Wall on November 9, 1989. And with it, its own demise. Nine days after the unexpected opening of the border, the GDR's secret police was renamed the Office for National Security (AfNS). New name, old system — that's how the overwhelming majority of the 17 million East Germans saw it.

On January 15, 1990, the Stasi was the main topic of discussion at the meeting of the Central Round Table in Berlin. At these meetings, representatives of the old regime led by head of government Hans Modrow met with civil rights activists to discuss the future of the ailing GDR. That day, the New Forum political movement called for a rally in front of the Stasi headquarters. "Bring lime and bricks!" read one leaflet. The secret service was to be symbolically bricked up and the huge area was to be overrun "with imagination and without violence."

Thousands of people answered the call, including Arno Polzin from East Berlin. There was one thing that the then 27-year-old toolmaker will never forget: "The fact that we were allowed onto the site unchallenged." No resistance, no controls — or was it a trap? When he entered the site, which had been hermetically........

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