Konnilyn Feig, Hitler's Death Camps, New York, Holmes and Meier, 1981.
Before the Nazis developed the killing centers and extermination camps, they used the Einsatzgruppen to kill the Jews and other undesirables. But those massacres showed that there were glaring problems inherent in the extermination of masses of people, among them were the need of speed, efficient and complete body removal, secrecy, and disposal of belongings. Killing centers, however, provided both expediency and secrecy, and the later extermination camps made possible the full range of physical and psychological abuse that the Nazis wished to employ in the destruction of the undesirables.
Himmler designed the killing centers exclusively as places of secret and instant death. Today there is widespread misunderstanding and ignorance about the four killing centers, which were all on isolated occupied Polish territory and had short histories. Writers often confuse the centers with the camps. Very few people survived the centers, and those who did have seldom written about them; almost nothing remains of the centers; few people have visited them; all are located deep in rural Poland, and the Polish government would like them to remain obscure because they are reminders of a separate form of dying for Jews -- these factors all contribute to the confusion. The key to understanding is that the killing centers were only killing centers -- they had no other function. The prisoners there did not die on the way to death -- they were killed.
In 1941 Himmler called in his gassing specialist, Christian Wirth, known as the Technocrat of Destruction, and ordered him to design and implement an extermination program with Chelmno as the pilot project. Sometime in 1941 Hitler gave the verbal order for the Final Solution, treating it as a secret of the highest order. Hitler and Himmler created Operation Reinhard -- the camouflage term for the Belzec, Sobibor, and Treblinka program -- under the command of Odilo Globocnik. Instead of reporting to the SS-WVHA, as did Majdanek, Auschwitz, and other concentration camps, Operation Reinhard reported to the office of the Fuhrer -- the Reich Chancellery Office. Although keeping the control of the program close to him, Hitler delegated responsibility for the practical aspects to Himmler. The staff turned to the euthanasia program (T-4) for ideas and trained personnel. They selected the sites and sent out construction teams. T-4 construction workers helped with the buildings. And high-level T-4 personnel came to the centers after the revolts to deliver funeral operations for their fallen SS comrades.
Operation Reinhard German camp workers were not told of the program goals and their precise duties until they reached the centers. Upon their arrival the SS officers oriented them by comparing center goals with the euthanasia program, which was very familiar to the workers. Then the SS swore them to absolute secrecy. Each worker signed a pledge that contained the following commitments:
1. I have been instructed that under no circumstances will I discuss with anyone outside or with co-workers anything dealing with the operation
2. I understand the top secrecy of any of the occurences of the so-called "Jewish Relocation"
3. I may not take any pictures
4. I promise to keep my word to the best of my ability
5. I understand that after completion of my service, this oath of secrecy will still apply [footnote 38]
Operation Reinhard issued in a new phase of mass murder. Himmler replaced the mobile killing units with stationary death factories, and the gas chamber period began. The authorities had no intention of accomodating prisoners in the killing centers for any length of time -- they exterminated them almost immediately upon arrival. Administrative structures were very simple. Because the centers were never linked to the war effort, only minimal industrial activity existed. And most inmates or transients were Jews, although there were some Polish Christians.
The Nazis built Sobibor, Belzec, Treblinka, and Chelmno as killing centers for the sole purpose of extermination the Jews of Europe and as many Gypsies as could be found. All four were constructed on Polish soil primarily because of the widespread Polish railway system, which had stations in the smallest towns. In addition, the Polish countryside, which was densely forested and thinly populated, made secrecy possible. Not one killing center existed longer than seventeen months. The SS obliterated each of them, intending to remove all traces. Polish scholars estimate conservatively that in these four camps, 2,000,000 Jews and 52,000 Gypsies, one third of whom were children, were killed. Yes, the concentration camps had their gas vans, their gas chambers, their crematoria, and their mass graves. People were shot in them, given injections, gassed, and hundreds of thousands died of starvation and disease. But even in Birkenau, where some have estimated that 1,000,000 Jews were killed, there was a chance of life. In the killing centers the only inmates kept alive for a short time were those selected to process the bodies of their fellow Jews.
First came Chelmno -- the pilot extermination project -- rude and crude, conferring death by three gas vans, borrowed from the Eastern Front. No crematoria, just mass graves in the woods. Chelmno exemplified extermination in the primitive style. Then came Belzec with its diesel-run gas chambers, which were inefficient and time consuming, and its primitive open-pit burning to dispose of the bodies. Sobibor, in a small and obscure corner of Poland, was next. It too had gas chambers and mass graves.
And finally came Treblinka. Learning from the mistakes at the other three, Nazis were here able to construct an unusually efficient destruction instrument that managed to destroy the lives and bodies of 1,000,000 human beings in only twelve months -- a truely monsterous carnage. In order to create a killing center with such efficiency, it was necessary to invent the killing machinery and process. And for that, the SS technicians and experts had no precedents on which to rely. They had to depend on original thinking to accomplish the task. It was at Treblinka that the technicians finally triumphed over the insurmountable difficulties of secretly destroying the lives, bodies, and posessions of huge numbers of people in a short period of time [footnote 39].
After the Solibor Revolt, Himmler ordered the centers closed. He sent the German camp personnal to the Trieste area on the Adriatic Coast, to continue the operation there. Assigned to a group known as the Arm Unit, the men's task was to carry out the technical preparation for the mass killing of Jews in that area. In a rice factory near Trieste they set up a burning facility. Partesian activity, however, made program implementation impossible. On November 4, 1943, Globocnik wrote to Himmler from Trieste: "I have on Oct. 19, 1943 completed Action Reinhard and closed all the camps." He asked for special medals for his men in recognition of their "specially difficult task." Himmler responded warmly to "Globos" on November 30, 1943, thanking him for carrying out Operation Reinhard. By the end of the war, partesians had killed Wirth and Sobibor Commandant Reichleitner, Globocnik commited suicide" [footnote 40].
 Ruckerl, 120-126; oath 125-126
 Ruckerl, NS-Prozesse, 35-42
 Ruckerl, 130-131
Ruckerl, Adalbert, hrsq.; NS-Prozesse. Karlsruhe: Verlag C. F. Muller, 1972