Genocide is the mass killing of a population. Historically, the act has been committed against populations based on religious beliefs, politics, and/or ethnicity. In the modern era, engaging in genocide is considered an international war crime and a crime against humanity.
During World War II, genocide was committed by the Nazis against the European Jewish population. Jews were imprisoned in concentration camps in which some were worked to death, others were killed through exposure to toxic gases, and still others were beaten or shot to death. Genocide may be as devastating as war in terms of death toll but is different in that it is committed against civilians and prisoners who do not necessarily have any formal military training. Genocide is also performed without consideration of the age of its victims.