two squads of SS soldiers responsible for overseeing the prisoners. Within the extermination camps, the Blockführer was in charge of the prisoner Sonderkommando and was also the person who would physically gas victims in the camp's gas chambers. The Jewish Sonderkommando workers in turn, were terrorised by up to around 100 mostly collaborator Trawniki men per camp, called Wachmannschaften (security guards or watchmen). The camp perimeter and watch towers were overseen by a separate formation called the Wachbattalion (guard battalion). The guard battalion commander was responsible for providing watch bills to man guard towers and oversaw security patrols outside the camp. The battalion was organized on typical military lines with companies, platoons, and squads. The battalion commander was subordinate directly to the camp commander. Concentration camps also had supply and medical personnel, attached to the headquarters office under the camp commander, as well as a security office with Gestapo and Kripo personnel attached to the camp. Heydrich had been successful in getting control over the "political departments" of the camps. These security personnel were under direct command of Sicherheitspolizei (SiPo) commanders until September 1939 and thereafter, the Reich Security Main Office (Reichssicherheitshauptamt, RSHA) commanders independent of the camps. In addition to the regular SS personnel assigned to a concentration camp, there also existed a prisoner system of trustees known as Kapos who performed a wide variety of duties from administration to overseeing other groups of prisoners. The Sonderkommandos were special groups of Jewish prisoners who assisted in the extermination camps with the disposal of bodies and other tasks. The duty of actually gassing prisoners was, however, always carried out by the SS. The Holocaust In 1942 Glücks was increasingly involved in the administration of the Endlösung, supplying personnel to assist in Aktion Reinhardt (although the death camps of Belzec, Treblinka and Sobibor were administered by SS-und Polizei-führer Odilo Globocnik of the General Government). In July 1942, Glücks met Himmler to discuss medical experiments on concentration camp inmates. All extermination orders were issued from Glücks' office to SS-TV commands throughout Nazi Germany and occupied Europe. He specifically authorized the purchase of Zyklon B for use at Auschwitz. Already in 1943 the SS-TV units began to receive orders to conceal as much of the evidence of the Holocaust as possible. Himmler was most concerned about covering up Nazi crimes ever since the Polish 22,000 victims of the Soviet Katyn massacre were discovered