Majdanek, or KL Lublin, was a German concentration and extermination camp built and operated by the SS on the outskirts of the city of Lublin during the German occupation of Poland in World War II.
 Although initially purposed for forced labor rather than extermination, the camp was used to kill people on an industrial scale during Operation Reinhard, the German plan to murder all Jews within their own General Government territory of Poland.
 The camp, which operated from October 1, 1941, until July 22, 1944, was captured nearly intact, because the rapid advance of the Soviet Red Army during "Operation Bagration" prevented the "SS" from destroying most of its infrastructure, and the inept Deputy Camp Commandant Anton Thernes failed in his task of removing incriminating evidence of war crimes.
 Therefore, Majdanek became the first concentration camp discovered by Allied forces.
 Also known to the "SS" as "Konzentrationslager Lublin", Majdanek remains the best preserved Nazi concentration camp of the Holocaust.
The Kraków Ghetto was one of five major, metropolitan Jewish ghettos created by Nazi Germany in the new General Government territory during the German occupation of Poland in World War II.
 It was established for the purpose of exploitation, terror, and persecution of local Polish Jews, as well as the staging area for separating the "able workers" from those who would later be deemed unworthy of life.
 The Ghetto was liquidated between June 1942 and March 1943, with most of its inhabitants sent to their deaths at Bełżec extermination camp as well as Płaszów slave-labor camp, and Auschwitz concentration camp, 60 km rail distance.
The Jasenovac concentration camp (/Логор Јасеновац, ] ; Yiddish: יאסענאוואץ‎ ) was an extermination camp established in Slavonia by the authorities of the Independent State of Croatia (NDH) during World War II.
 The camp was established by the governing Ustaše regime and not operated by Nazi Germany.
 It was one of the largest concentration camps in Europe and the camp has been referred to as "the Auschwitz of the Balkans" and "the Yugoslav Auschwitz".
Auschwitz concentration camp (German: "Konzentrationslager Auschwitz" , ] , also "KZ Auschwitz " or "KL Auschwitz ") was a network of German Nazi concentration camps and extermination camps built and operated by the Third Reich in Polish areas annexed by Nazi Germany during World War II.
 It consisted of (the original camp), Auschwitz II–Birkenau (a combination concentration/extermination camp), (a labor camp to staff an IG Farben factory), and 45 satellite camps.
Monowitz (also called Monowitz-Buna or Auschwitz III) was initially established as a subcamp of Nazi Germany's Auschwitz concentration camp.
 It was one of the three main camps in the Auschwitz concentration camp system, with an additional 45 subcamps in the surrounding area.
 It was named after the village of Monowice (German: Monowitz) upon which it was built and was located in the annexed portion of Poland.
 The SS established the camp in October 1942 at the behest of I.G. Farben executives to provide slave labor for their Buna Werke (Buna Works) industrial complex.
 The name "Buna" was derived from the butadiene-based synthetic rubber and the chemical symbol for sodium (Na), a process of synthetic rubber production developed in Germany.
 Various other German industrial enterprises built factories with their own subcamps, such as Siemens-Schuckert's Bobrek subcamp, close to Monowitz in order to profit from the use of slave labor.
 The German armaments manufacturer Krupp, headed by SS member Alfried Krupp, also built their own manufacturing facilities near Monowitz.
Hanns Alexander (6 May 1917 – 23 December 2006) was a German Jewish refugee who tracked down and arrested the Kommandant of Auschwitz Rudolf Höss.
Rudolf Höss (also Höß, Hoeß or Hoess; 25 November 1901 – 16 April 1947) was a Nazi German "SS"-"Obersturmbannführer" (lieutenant colonel) and the longest-serving commandant of Auschwitz concentration and extermination camp in World War II.
 He tested and carried into effect various methods to accelerate Hitler's plan to systematically exterminate the Jewish population of Nazi-occupied Europe, known as the "Final Solution".
 On the initiative of one of his subordinates, SS-"Hauptsturmführer" (captain) Karl Fritzsch, Höss introduced pesticide Zyklon B containing hydrogen cyanide to the killing process, thereby allowing SS soldiers at Auschwitz to murder 2,000 people every hour.
 He created the largest installation for the continuous annihilation of human beings ever known.
Sobibór (or Sobibor , or , ] ) was a Nazi German extermination camp built and operated by the SS near the railway station of Sobibór during World War II, within the semi-colonial territory of General Government of the occupied Second Polish Republic.
 The camp was part of the secretive Operation Reinhard, which marked the deadliest phase of the Holocaust in German-occupied Poland.
 The camp was situated near the rural county's major town of Włodawa (called "Wolzek" by the Germans), 85 km south of the provincial capital, Brest-on-the-Bug (Brześć nad Bugiem in Polish).
 Its official German name was "SS-Sonderkommando Sobibór".
 Jews from Poland, France, Germany, the Netherlands, Czechoslovakia and the Soviet Union (including Jewish-Soviet POWs), were transported to Sobibór by rail.
 Most were suffocated in gas chambers fed by the exhaust of a large petrol engine.
 Up to 200,000 people were murdered at Sobibór and possibly more.
 At the postwar trial against the former "SS" personnel of Sobibór, held in Hagen two decades into the Cold War, Professor Wolfgang Scheffler estimated the number of murdered Jews totalled a minimum of 250,000.
 This would make it the fourth worst extermination camp, after Bełżec, Treblinka, and Auschwitz.
The SS command of Auschwitz concentration camp refers to those units, commands, and agencies of the German SS which operated and administered the Auschwitz concentration camp during World War II.
 Due to its large size and key role in the Nazi genocide program, the Auschwitz Concentration Camp encompassed personnel from several different branches of the SS, some of which held overlapping and shared areas of responsibility.
Birkenau commonly refers to the Nazi German extermination camp Auschwitz II–Birkenau in the Auschwitz concentration camp during World War II, located near Brzezinka, Poland.

Question: Who tracked down and arrested the longest-serving commandant of Auschwitz concentration and extermination camp?
Answer: Hanns Alexander