Why do some Jews who survived the Holocaust have a number tattooed on their arm?

Memorial Ceremony at the Raoul Wallenberg square in Stockholm with Holocaust survivors. 27 January 2013, International Holocaust Remembrance Day. Photo Credit: Wikimedia Commons (Frankie Fouganthin)

The Auschwitz camp complex was the only institution to systematically tattoo inmates with their prison numbers, to facilitate their identification after death from starvation, disease or brutality in the camp. Incoming prisoners were assigned a camp serial number, which was also sewn to their prison uniforms.

By the end of the war, the camp authorities were using nine different numbering sequences. These identified particular inmates as belonging to particular racial or ethnic groups.

Only those prisoners selected for work were issued serial numbers; those sent directly to the gas chambers immediately on arrival were not registered and received no tattoos.