Rudolf Hoess, the barbaric Commandant of Auschwitz, was a model of efficiency.
Those who were selected for "death" went to a barracks, ostensibly for "de-lousing." They were rushed naked – whatever the season of the year or weather conditions – amidst shouting and beatings to the nearby bathhouse.
There their heads were shaved and all body hair removed, most frequently with dull razors, which caused acute pain.
They then entered large shower-like chambers, some which could "process" 2,000 people at once.
The doors were locked tight and Zyklon-B gas was pumped through the “shower-heads.” The gas would usually kill everyone within five minutes.
Afterwards, Jewish slaves (called Sonderkommando) would take out the bodies, check for gold, and then put the corpses into the crematoria.
They worked to burn the corpses, stoke the fires, drain body fat, and turn over the "mountain of burning corpses" for even combustion and a peak fire-temperature. These prisoners were well aware that they, too, would meet exactly the same fate.
Those ovens worked day and night. The doors literally melted off the hinges.
At one point, 20,000 people a day were being murdered at Auschwitz.
With perfect German efficiency, everything was utilized: Human hair for stuffing coats and mattresses, and human ash for fertilizer.
During the war, the Nazis made the surviving Jews pay for everything. If someone’s relative was carted away to the camps, he would get a postcard informing him that he died of a heart attack, and if he would kindly send 3-1/2 Marks, they would send his ashes.
Nazi "doctors" conducted horrible experiments on the Jews in their power.
God forbid, if someone ever became sick, he would end up in a concentration camp "hospital," where those same medical monsters who supervised the selection on the platforms, who had sworn to "help humanity," conducted "medical research."
They would do sadistic acts such as placing Jews in ice baths, then monitoring them until they died. Why? Since some German pilots might end up in the water when fighting the Allies, these German “doctors” wanted to help the war effort by understanding how to prevent hypothermia.
Sometimes the "research" had no relevance to the war. Mengele, the infamous Angel of Death, "specialized" in bizarre experimentation on twins and dwarfs, ostensibly to better direct Aryan genetics. Victims were injected with diseases, then killed with a chloroform injection to the heart, dissected and compared.
The Nazi bestiality knew no limits. Some had chemicals dripped into their eyes to change eye color. Children were surgically sewn together to create Siamese twins.