"Kemal" had a good knowledge of German and even though he wasn't a member of any political party, he was sympathetic to socialist ideals. In the spring of 1981, he needed help. His residency permit for West Berlin was about to expire and he was on the verge of getting deported to Turkey. These circumstances made Kemal an attractive candidate for the East German secret police, or Stasi, which promptly took advantage of the situation.

"They arranged a German wife for him and allowed her to move to West Berlin. As a guest worker with a German wife, he was then able to stay in West Berlin," Birthler Authority researcher Georg Herbstritt told Deutsche Welle.

Herbstritt said this was a typical method used by the Stasi to recruit foreigners living in West Germany, where they served as low-level spies for the East. The Birthler Authority estimates that five percent of the Stasi's so-called "unofficial collaborators" during the 1980s were foreigners.

Marriage bait

In some cases, Stasi officials would hook new recruits by threatening to bust them for infractions of East German laws during visits -- like crossing the border back to West Germany too late at night or for exchanging money on the black market or even if they had inadvertently taken a snapshot of a Stasi building.

Many of the Turkish men were assigned as so-called "fly catchers": they were supposed to inform the Stasi about East German women who were trying to marry foreigners in order to leave East Germany. More than 6,000 West Berlin Turks made day trips to the other side of the Berlin Wall during the 1980s, and they were popular targets for East German women looking for a better life.

Despite its eagerness to work with foreigners, the Stasi often held a prejudicial view of them. In the 1970s, then East German State Security Minister Erich Mielke expressed his fear that foreigners coming in from West Berlin included "many anti-social and criminal" types who could pose a threat to security during their visits there.

Officials feared airplane hijackings, attacks against embassies and even drug smuggling. The tensions at the time between Turkish and other foreign groups in West Berlin fuelled those emotions. Because Turks were -- and still are -- the largest minority group in Germany, they made up the majority of the Stasi's foreign collaborators.

Little known

Though there has been little public discussion over the foreigners working for the Stasi, there have been some low-profile court cases. But most of the accused got off lightly without anyone having to sit out a jail sentence, Herbstritt said.

That's because few foreigners serving as top spies. Non-Germans just didn't have the access. Nor did they have the opportunity to make a career in politics or the military. They often came as simple laborers to Germany and the Stasi deployed them where they could be useful.

But they haven't escaped the notice of history, with Herbstritt now compiling research on this unplumbed aspect of Germany's Cold War years.