The Holocaust, or more properly the operation of the six Nazi extermination camps sited in Poland that within in a brief period of some eighteen months from 1942 killed and processed the great majority of victims, has always presented a scale of logistics that otherwise intelligent people have found improbable. It really wasn't. The evidence of how the thing worked is comprehensive and utterly credible.
The key was the humble cattle truck, mainstay of armies everywhere, marked for 8 horses or 40 men. A single train could transport a entire regiment, its kit and its support branches. Jews were packed at the rate of between 50 - 150 per wagon, and a formation (a train) could have a consist of 55 wagons. Once the formation had come to a halt at the unloading ramps and the doors unlatched, it took little effort to disembark the cargo - they would be eager for release from those stinking hells. Shouting and whips would separate the men from the women, then into the undressing sheds, then into the death chamber. At Treblinka an entire train could be killed within two to three hours. Burning the dead in batches of 800 - 1,000 on the 'roasts' could be left to the Jewish work parties, who kept the fires burning constantly.
At one train a day, the operation would run smoothly; for the German managers, a hectic, noisy, stressful couple of hours until the cargoes had been gassed, then back to the peace and quiet of birdsong. Of course there would be days after distant SS units had liquidated entire ghettoes; Radom or Kielce, when the trains just kept coming, the German managers missed their meals, and the unburned dead just piled up. In the mess afterwards, over a few beers, they would gripe at such poor planning, just like car-plant middle managers tasked with a large export order at short notice.
Oh yes. It all worked very efficiently indeed. Franz Stangl, who commanded Treblinka, was even proud of his 'humane' approach, disguising the buildings and views so as to avoid stress to the condemned cargoes, just like any good abattoir manager. He was never personally cruel, never hit or shot or whipped anyone. He was diligent in doing the job assigned him - of killing and disposing of the contents of the trains sent to his camp as efficiently as possible.
Perhaps most poignant is the use the Nazis made of the Jews themselves, as ghetto police who assisted in the round-ups and train loadings, as camp kapos running the recovery of gold and hair and spectacles and shoes, as overseers of the roasts. Treblinka processed the whole of the Warsaw ghetto in just three months, between July and September 1942. The very last transport, just a dozen wagons, ten days after the bulk liquidation, was reserved for the Jewish ghetto police.