The camp commandant, Rudolf Höss, testifed at the Nuremberg Trials that up to 2.5 million people had died at Auschwitz. The Auschwitz-Birkenau State Museum revised this figure in 1990, and new calculations now place the figure at 1.1–1.6 million,^[2][3] about 90 percent of them Jews from almost every country in Europe.^[4] Most of the dead were killed in gas chambers using Zyklon-B; other deaths were caused by systematic starvation, forced labor, lack of disease control, individual executions, and so-called medical experiments.

Beginning in 1940, Nazi Germany built several concentration camps and an extermination camp in the area, which at the time was under German occupation. The Auschwitz camps were a major element in the perpetration of the Holocaust; at least 1.1 million people were killed there, of whom over 90% were Jews.

The three main camps were:

• Auschwitz I, the original concentration camp which served as the administrative center for the whole complex, and was the site of the deaths of roughly 70,000 people, mostly Poles and Soviet prisoners of war.
• Auschwitz II (Birkenau), an extermination camp, where at least 1.1 million Jews, 75,000 Poles, and some 19,000 Roma (Gypsies) were killed.
• Auschwitz III (Monowitz), which served as a labor camp for the Buna-Werke factory of the I.G. Farben concern.

See list of subcamps of Auschwitz for others.

Like all German concentration camps, the Auschwitz camps were operated by Heinrich Himmler's SS. The commandants of the camp were the SS-Obersturmbannführers Rudolf Höß (often written "Hoess") until the summer of 1943, and later Arthur Liebehenschel and Richard Baer. Höß provided a detailed description of the camp's workings during his interrogations after the war and also in his autobiography. He was hanged in 1947 in front of the entrance to the crematorium of Auschwitz I. Command of the women's camp, which was separated from the men's area by the incoming railway line was held in turn by Johanna Langefeld, Maria Mandel, and Elisabeth Volkenrath.

Auschwitz I served as the administrative center for the whole complex. It was founded on May 20, 1940, on the basis of an old Polish brick army barracks (originally built by the Austro-Hungarian Empire). A group of 728 Polish political prisoners from Tarnów became the first residents of Auschwitz on June 14 that year. The camp was initially used for interning Polish intellectuals and resistance movement members, then also for Soviet Prisoners of War. Common German criminals, "anti-social elements" and 48 German homosexuals were also imprisoned there. Jews were sent to the camp as well, beginning with the very first shipment (from Tarnów). At any time, the camp held between 13,000 and 16,000 inmates; in 1942 the number reached 20,000. The entrance to Auschwitz I was—and still is—marked with the ironic sign “Arbeit Macht Frei”, or “work (will) make (you) free.”

The SS selected some prisoners, often German criminals, as specially privileged supervisors of the other inmates (so-called: kapo). The various classes of prisoners were distinguishable by special marks on their clothes; Jews were generally treated the worst. All inmates had to work in the associated arms factories; except Sundays, which were reserved for cleaning and showering and there were no work assignments.

The harsh work requirements, combined with poor nutrition and hygiene, led to high death rates among the prisoners. Block 11 of Auschwitz (the original standing cells and such were block 13) was the "prison within the prison", where violators of the numerous rules were punished. Some prisoners were made to spend the nights in "standing-cells". These cells were about 1.5 metres square, and four men would be placed in them; they could do nothing but stand, and were forced during the day to work with the other prisoners. In the basement were located the "starvation cells"; prisoners incarcerated here were given neither food nor water until they were dead. Also in the basement were the "dark cells"; these cells had only a very tiny window, and a solid door. Prisoners placed in these cells would gradually suffocate as they used up all of the oxygen in the air; sometimes the SS would light a candle in the cell to use up the oxygen more quickly. Many were subjected to hanging with their hands behind their backs, thus dislocating their shoulder joints for hours, even days.

The execution yard is between blocks 10 and 11. In this area, prisoners who were thought to merit individual execution received it. Some were shot, against a reinforced wall which still exists; others suffered a more lingering death by being suspended from hooks set in two wooden posts, which also still exist.

Auschwitz II (Birkenau)

Construction on Auschwitz II (Birkenau) began in October 1941 to ease congestion at the main camp. It was designed to hold several categories of prisoners, and to function as an extermination camp in the context of Himmler's preparations for the Final Solution of the Jewish Question.^[6]

Many people know the Birkenau camp simply as "Auschwitz"; it was larger than Auschwitz I, and more people passed through its gates than did those of Auschwitz I. It was the site of imprisonment of hundreds of thousands, and of the killing of over one million people, mainly Jews but also large numbers of Poles, and Gypsies, mostly through gassing.

Birkenau had four gas chambers, designed to resemble showers, and four crematoria, used to incinerate bodies. Approximately 40 more satellite camps were established around Auschwitz. These were forced labor camps and were known collectively as Auschwitz III. The first one was built at Monowitz and held Poles who had been forcibly evacuated from their hometowns by the Nazis. The inmates of Monowitz were forced to work in the chemical works of IG Farben.

Prisoners were transported from all over German-occupied Europe by rail, arriving at Auschwitz-Birkenau in daily convoys. Arrivals at the complex were separated into four groups:

• One group, about three-quarters of the total, went to the gas chambers of Auschwitz-Birkenau within a few hours; they included all children, all women with children, all the elderly, and all those who appeared on brief and superficial inspection by an SS doctor not to be fully fit. In the Auschwitz Birkenau camp more than 20,000 people could be gassed and cremated each day. At Birkenau, the Nazis used a cyanide gas produced from Zyklon B pellets, which were manufactured by two companies who had acquired licensing rights to the patent held by IG Farben. The two companies were Tesch & Stabenow, of Hamburg, who supplied two tons of the crystals each month, and Degesch, of Dessau, who produced three-quarters of a ton. The bills of lading were produced at Nuremburg.^[7]
• A second group of prisoners were used as slave labor at industrial factories for such companies as IG Farben and Krupp. At the Auschwitz complex 405,000 prisoners were recorded as slaves between 1940 and 1945. Of these about 340,000 perished through executions, beatings, starvation, and sickness. Some prisoners survived through the help of German industrialist Oskar Schindler, who saved about 1,100 Polish Jews by diverting them from Auschwitz to work for him, first in his factory near Kraków and later at a factory in what is now the Czech Republic.
• A third group, mostly twins and dwarfs, underwent medical experiments at the hands of doctors such as Josef Mengele, who was also known as the “Angel of Death.”
• The fourth group was composed of women who were selected to work in "Canada", the part of Birkenau where prisoners' belongings were sorted for use by Germans. The name "Canada" was very cynically chosen. In Poland it was - and is still - used as an expression used when viewing, for example, a valuable and fine gift. The expression comes from the time when Polish emigrants were sending gifts home from Canada.

The camp was staffed partly by prisoners, some of whom were selected to be kapos (orderlies) and sonderkommandos (workers at the crematoria). The kapos were responsible for keeping order in the barrack huts; the sonderkommando prepared new arrivals for gassing (ordering them to remove their clothing and surrender their personal possessions) and transferred corpses from the gas chambers to the furnaces, having first pulled out any gold that the victims might have had in their teeth. Members of these groups were killed periodically. The kapos and sonderkommandos were supervised by members of the SS; altogether 6,000 SS members worked at Auschwitz.

By 1943 resistance organizations had developed in the camp. These organizations helped a few prisoners escape; these escapees took with them news of exterminations, such as the killing of hundreds of thousands of Jews transported from Hungary between May and July 1944. In October 1944 a group of sonderkommandos destroyed one of the crematoria at Birkenau. They and their accomplices, a group of women from the Monowitz labor camp, were all put to death. It was also not uncommon if one prisoner escaped, selected persons in the escapee's block were killed.

When the Soviet army liberated Auschwitz on January 27, 1945, they found about 7,600 survivors abandoned there. More than 58,000 prisoners had already been evacuated by the Nazis and sent on a final death march to Germany. In 1947, in remembrance of the victims, Poland founded a museum at the site of the Auschwitz concentration camp. By 1994, some 22 million visitors — 700,000 annually — had passed through the iron gate crowned with the cynical motto, "Arbeit macht frei" ("Work will set you free").

Auschwitz III and satellite camps

Also see List of subcamps of Auschwitz

The surrounding work camps were closely connected to German industry and were associated with arms factories, foundries and mines. The largest work camp was Auschwitz III Monowitz, named after the Polish village of Monowice. Starting operations in May 1942, it was associated with the synthetic rubber and liquid fuel plant Buna-Werke owned by I. G. Farben. In regular intervals, doctors from Auschwitz II would visit the work camps and select the weak and sick for the gas chambers of Birkenau. The largest subcamps were built at Trzebinia, Blechhammer and Althammer. Female subcamps were constructed at Budy , Plawy, Zabrze, Gleiwitz I, II, III, Rajsko and at Lichtenwerden (now Světlá).

The whole Auschwitz complex of camps was liberated in early 1945 by the advancing Russian army.

Some information regarding Auschwitz reached the Allies during 1941–1944, such as the reports of Witold Pilecki and Jerzy Tabeau, but the claims of mass killings were generally dismissed as exaggerations. This changed with receipt of the very detailed report of two escaped prisoners, Rudolf Vrba and Alfred Wetzler, which finally convinced most Allied leaders of the truth about Auschwitz in the middle of 1944.

Detailed air reconnaissance photographs of the camp were taken accidentally during 1944 by aircraft seeking to photograph nearby military-industrial targets, but no effort was made to analyse them. (In fact, it was not until the 1970s that these photographs of Auschwitz were looked at carefully.)

Starting with a plea from the Slovakian rabbi Weissmandl in May 1944, there was a growing campaign to convince the Allies to bomb Auschwitz or the railway lines leading to it. At one point Winston Churchill ordered that such a plan be prepared, but he was told that bombing the camp would most likely kill prisoners without disrupting the killing operation, and that bombing the railway lines was not technically feasible. Later several nearby military targets were bombed. One bomb accidentally fell into the camp and killed some prisoners. The debate over what could have been done, or what should have been attempted even if success was unlikely, has continued heatedly ever since