In the western Polish town of Kalisz, a huge black truck drove up to the Jewish old age home and took away a load of Jews. The truck left, and reappeared several times that weekend, until all the Jews had been emptied from the old age home. When the Jewish community demanded to know where they had been taken, they were told that the old people had been "relocated." It did not take long for people to notice that the truck's exhaust system was connected to the cargo compartment. The Jews had been asphyxiated as the truck drove, then their bodies had been burned or buried.

U.S. troops watch a passing cart laden with corpses intended for burial leave the compound of the Dachau concentration camp.

This method of execution was cheap and efficient, but limited in scale. The first death camps were built around the same method of execution by carbon monoxide asphyxiation. The camps of Belzec, Sobibor, and Treblinka were outfitted with airtight buildings connected to turbine engines that pumped out carbon monoxide gas. Then the Jews were rounded up for "relocation." In the words of an eyewitness, which were used as evidence during the Nuremburg trials:

"The following morning, a little before seven, there was an announcement: 'The first train will arrive in ten minutes!' A few minutes later a train arrived from Lemberg: 45 cars with more than 6,000 people. Two hundred Ukrainians...flung open the doors and drove the Jews out of the cars with leather whips. A loudspeaker gave instructions: 'Strip, even artificial limbs and glasses. Hand all money and valuables in at the valuables window.' Then the march began. Barbed wire on both sides, in the rear two dozen Ukranians with rifles....A tall SS man in the corner called to the unfortunates, 'Nothing is going to hurt you! Just breathe deep and it will strengthen your lungs....' They climbed little wooden stairs and entered the death chambers without resistance....The doors closed....[They] tried to start the motor. It wouldn't start!...70 minutes, and the Diesel still would not start! The people were waiting in the gas chambers. You could hear them weeping....The Diesel started after 2 hours and 49 minutes....All were dead after thirty-two minutes! Jewish workers on the other side opened the wooden doors. They had been promised their lives in return for doing this horrible work, plus a small percentage of the money and valuables collected. The people were still standing, like columns of stone, with no room to fall or lean. Even in death you could tell the families, all holding hands....Dentists knocked out gold teeth....They told me that they poured Diesel oil over the bodies and burned them on railroad ties to make them disappear."

600,000 Jews were murdered at Belzec, 250,000 at Sobibor, 750,000 at Treblinka, and 300,000 at Chelmno.

Auschwitz-Birkenau

Crematoria ovens in Buchenwald concentration camp.

The largest, and most infamous, death camp was at Auschwitz, Poland. The camp was so large that it was divided into three major sections, and dozens of branch camps. By 1942 it held at least 150,000 prisoners awaiting death and 3,000 SS guards. As many as four trains arrived a day, from all across Europe. The prisoners were sorted into two lines; one led to imprisonment for slave labor, the other led to death. The executions were frequently disguised as "disinfectant showers;" the prisoners left their clothes on hooks, and were handed bars of soap. Only after the airtight doors were sealed shut and the canisters of poison gas were dropped in through holes in the ceiling did they realize their fate. The gas chambers at Auschwitz were outfitted with the highly toxic gas Zyklon B, initially designed for the extermination of insects. The gas was 100% fatal within three to five minutes. The bodies were then robbed of anything of value: hair was shaved off the bodies of the women, and jewelry and gold teeth were removed from the corpses. The camp's gas chambers were augmented with four crematories with 46 ovens. Nearby cities were frequently covered with a snow of human ash. The Nazis sometimes killed 12,000 to 15,000 people each day in the Auschwitz-Birkenau complex. In all, two million people were murdered at this camp.

The Nazis attempted to keep these exterminations secret even from their own officers. It was not hard to guess, however, what was happening to the millions of people transported into these camps. Himmler addressed a small group of SS chiefs in 1943, saying:

"I should like to talk about the evacuation of the Jews, about the extermination of the Jewish people....Most of you know what it is like to see a pile of 100 corpses.... This is a glorious page in our history, never before, never again to be written."