Eugenics programs to control reproduction and purge supposedly inferior populations from the population were a cornerstone of Nazi policy. In the Third Reich, they predated the ghettos, concentration camps and mass exterminations that characterized the latter part of the war. However, the Nazis did not stop at forcible sterilization; instead, they trained willing nurses to starve and kill patients; the murders were euphemistically called a "euthanasia" program. This approach set the stage for what happened to the ill and elderly at the camps.

Selection Process

When prisoners first arrived at the camps, they were evaluated by doctors based on outward appearance and not medical examination. They determined who would live for the time being -- and who would be put to death right away. Nazi doctors took an extremely utilitarian approach. People they viewed as unfit to work were killed; able-appearing workers were spared for the moment.

Death by Labor

The conceit that some camps were labor camps while others were marked for extermination is not entirely correct. Extermination was the plan for all prisoners at every camp from Auschwitz to Bergen-Belsen by the latter years of the war. The question was whether or not prisoners would die of starvation-induced death by hard manual labor -- or be killed immediately. In other words, people worked until they died or became too sick to work. Many older people died in the course of performing slave labor.

Earliest Systematic Extermination

When judged to have no value to Nazis as slaves, the sick, disabled and old were murdered. At first, killings were conducted with prisoners standing or kneeling at the edge of mass graves, where they were shot in the head and fell into the graves. This practice persisted in some camps until the end, but was not generally favored by the Nazis, who regretted that it was emotionally taxing for German soldiers and noticed in some cases that the glut of corpses affected local water supplies.

Gassing and Ovens

The Nazis ultimately developed large gas chambers and ovens to kill the sick and the old -- and then dispense with their bodies -- much more quickly. The gas chambers were designed to appear like showers, and people selected for death were systematically loaded into them in groups -- and then gassed. Those who had been gassed were then cremated in mass ovens. These practices were widely expanded toward the end of the war as Nazis sought the complete extermination of European Jews.