Political prisoners (Schutzhäftlinge – Sch.), marked with a red triangle, sent to the camp on the basis of ‘protective custody orders’ (Schutzhaftbefehl) issued by the German state police. Political prisoners in Auschwitz were primarily Poles, Czechs, the French, Yugoslavs, Ukrainians and inmates registered as Russians as well as a small group of Germans and Austrians.

‘Criminal’ prisoners (Berufsverbrecher – BV), marked with a green triangle, sent to the camp directly after committing crime or after leaving prison in cases where the criminal police decided that the sentence issued by the court of law was too lenient. Prisoners of this category were usually Germans.

Asocial prisoners (Asoziale – Aso), marked with a black triangle, theoretically imprisoned for vagabondage or prostitution; in practice many other actions and behaviours were fairly freely interpreted by the German police authorities as ‘asocial’. Also the Roma were sent to the Gypsy camp in Birkenau officially for being ‘asocial’.

Jehovah’s Witnesses (Internationale Bibelforscher-Vereinigung – IBV), marked with a purple triangle, sent to the camp on account of their pacifist views, which in the Third Reich were regarded to be anti-state. Auschwitz prisoners of this category were primarily Poles and Germans.

Homosexuals (Homosexuelle, § 175), marked with a pink triangle, sent to the camp on the basis of section 175 of the German criminal code. Prisoners of this category at Auschwitz were Germans.

The Jews in Auschwitz were in fact a separate category of prisoner. They were most often registered as ‘political’ prisoners; cases of Jews appearing under different prisoner categories in camp documents are extremely rare. Initially they were distinguished from other political prisoners by having a yellow triangle with its base at the bottom underneath the inverted red triangle to form a Star of David. Later they had a narrow rectangular strip of yellow sewn above their red triangle. Jews who were sent to Auschwitz in 1944 and put into so-called transit camps received no prisoner numbers or triangles.

Soviet prisoners of war sent to Auschwitz in 1941 continued to wear their uniforms, but with an oil painted vertical stripe and the letters ‘SU’.

Correctional prisoners (Erziehungshäftlinge), chiefly Poles, marked with the letter ‘E’. Auschwitz was for them a kind of replacement correctional labour camp (Arbeiterziehungslager – AEL).

Police prisoners (Polizeihäftlinge), awaited their trials before a court martial in civilian clothes and they had no additional markings.