The Nazis represent the lowest point into the abyss of despicable behavior by carrying out a systematic extermination of a specific group of people, the Jews. The concentration camps by the end of the war were the most effective killing factories in history. When we look at our history with slavery and civil rights and political corruption, we know we will never go as far to the dark side as Nazi Germany. Driven by Hitler, the entire German population was convinced that getting rid of the Jews was the answer to their problems. Meanwhile thousands of SS officers participated in systematic killing of the Jews not because it was right, but because it was what they were told to do.
Nazi concentration camps started out in Germany as detention camps for political prisoners. The early camps were not built explicitly for Jews. In 1933 the first camp in Dachau was built, and people considered enemies of the state were sent there, including German Communists, Socialists, and Social Democrats. The term "concentration" meant that the imprisoned would be concentrated in one location as opposed to being dispersed in multiple prisons across Germany. It wasn't until years later that the camps became destinations for Jews.
Meanwhile, Jews in Germany systematically had their rights as citizens taken away. By 1935 Hitler had enacted the Nuremberg Laws which stripped Jews of their civil rights based on race. Jews were considered "non-Aryans". During this period Hitler was conscious of how Germany's policies would look to the world. Berlin hosted the 1936 Olympics, and they did allow German Jews to participate, thus avoiding an international boycott.
Hitler's plans accelerated as Germany annexed a willing Austria in 1938 and invaded Poland in 1939. Now Jews in Germany and its occupied lands were forced to live in segregated sections called ghettos, were forced to wear yellow stars called "Jew badges", and were stripped of all their possessions. Life in the ghettos was intolerable, as crowded conditions, malnutrition, and disease brought many deaths. Still Germany tried to make its treatment of Jews seem humane to the rest of the world, as International Red Cross inspectors were allowed to see the Jewish settlement of Theresienstadt in Czechoslovakia.
Meanwhile camps sprung up at an alarming rate after 1939. Some camps were labor camps, some were stopping points on the way to other camps. The most notorious death camps such as Auschwitz and Treblinka became operational by 1942. Jews were loaded onto trains with no idea where they were going, under the ruse of resettlement. The unknowing victims were actually charged for the one-way train tickets, and were given postcards to send back to the ghettos to assure family and friends they were ok. The killing started with Nazi squads arriving at camps and shooting the victims. Eventually the Nazis discovered they could use gas to kill more people and efficiently, and it would spare the Nazi shooters from emotional anguish. By the end of the war, the genocide of Jews was responsible for 5.8 million deaths, or about 1/2 of Europe's entire Jewish population.
As if the death camps were not cruel enough, the Nazis performed unthinkable human experiments on Jews. Led by Dr. Josef Mengele, some Jews were selected right off the trains at Auschwitz to be experimented on. Mengele was known as the "angel of death". Some of the experiments had the guise of helping with the war effort, such as being subjected to a tank of ice cold water for hours so the Germans could learn about the effects of hypothermia. Other experiments were performed to support the theory that the Aryan race was superior. They injected chemicals into the victims' eyes to see if their eye color would change. They injected them with malaria then tried to treat them various chemicals. They performed bone, muscle, and nerve transplants without anesthesia, causing the victims disfigurement and agony. Those who were killed in the gas chambers right away might be considered the lucky ones. Mengele somehow avoided capture after the war and lived for 30 more years in South America. We can only hope he lived out his years tormented by his actions in the war.
The range of human behavior can be looked at with the story of "Schindler's List", brought to life in the 1993 movie starring Liam Niesen. Oskar Schindler saved the lives of 1100 Jews by putting them to work in a factory that made defective weapons for the German army. What started as a money making operation for Schindler became a mission for doing the right thing against all odds. On the flip side, the character "Goth" in Schindler's List played by Ralph Fiennes represents the most base form of human behavior. Empowered as an SS lieutenant to do his part in the final solution, Goth is shown in the movie murdering people indiscriminately with seemingly no feeling at all. Did this character exist in the real concentration camps? Only those who survived the camps would know for sure.
When the war ended, the rest of the world found out about the horrors of the Nazi camps. Many of the Nazi officers were prosecuted for their crimes against humanity in the Nuremberg trials, which provided some retribution for the world. Survivors have had to live with the memories of torture and losing family members forever. Some have told their stories, while others continue to have those memories locked up in their own personal vault.