The system of classifying prisoners through the use of triangles (winkels) originated before the war in the concentration camps in Germany. In Auschwitz, they were implemented with certain modifications, but were not used at all for some groups of prisoners.
Red triangles marked “political prisoners (Schutzhäftlinge – Sch.), in other words, those who were imprisoned on the basis of a “protective custody order” (Schutzhaftbefehl) issued by a state police post. The political prisoners in Auschwitz were, above all, Poles.
Green triangles marked “criminal” prisoners (Berufsverbrecher - BV), imprisoned as a direct consequence of committing a forbidden act, or after release from prison in cases where the criminal police regarded the sentence imposed by the court as too lenient. Prisoners in this category were mostly Germans.
Black triangles marked “asocial” prisoners (Asoziale - Aso), imprisoned in theory for vagrancy or prostitution, but in fact for a wide range of other deeds or behaviors, loosely and arbitrarily interpreted by the police. The Roma in the Birkenau “Gypsy camp” were classified as asocial.
Purple triangles marked prisoners imprisoned for belonging to the Jehovah’s Witnesses (Internationale Bibelforscher-Vereinigung - IBV), regarded as enemies of the state because of their pacifistic beliefs.
Pink triangles marked homosexual prisoners, in practice exclusively German, who were imprisoned on the basis of §175 of the German criminal code.
In practice, Jews made up a separate prisoner category in Auschwitz. They were usually registered as “politicals”; the camp records contain extremely rare instances of Jews in other categories. At first, they were marked with an inverted red triangle overlapping a yellow triangle to form a Star of David shape; later, the red triangle was overlain with a narrow yellow rectangular stripe. Jewish prisoners transported to Auschwitz in 1944 and held temporarily in the so-called “transit camps” did not obtain either camp numbers or triangles.