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.
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. Although keeping the control of the program close to him, Hitler delegated responsibility for the practical aspects to Himmler. They selected the sites and sent out construction teams. Operation Reinhard German camp workers were not told of the program goals and their precise duties until they reached the centers.