The Holocaust

Jewish women wearing yellow badges in occupied France.

The Holocaust was a systematic, state-sponsored campaign of persecution and murder of six million Jewish men, women, and children by the Nazi regime and its collaborators. Nazi German authorities also targeted other groups based on perceived racial and biological inferiority, including the Roma, Germans with disabilities, certain groups of Slavic peoples, and groups persecuted based on political, ideological, and behavioral grounds. These included Communists, Socialists, Jehovah's Witnesses, and homosexuals. The number of victims killed during the Holocaust is uncertain, as many documents of the period were destroyed by Nazi officials to hide their crimes. But estimates range from 5.4 to 6 million European Jews were murdered, and another 3 to 5 million were murdered to total a range of 9 to 11 million people murdered during the Holocaust.

Nazi anti-Jewish propaganda

Between 1933 and 1945, Nazi Germany and its allies and collaborators implemented a wide range of anti-Jewish policies and measures, which varied from place to place. Not all Jews experienced the Holocaust the same way, but millions of people were persecuted because they identified as Jewish. This persecution took a variety of forms:

• Legal discrimination—this took the form of antisemitic laws, including the Nuremberg Race Laws and other discriminatory laws.
• Public identification and exclusion—these included antisemitic propaganda, boycotts of Jewish-owned businesses, public humiliation, and obligatory markings.
• Organized violence—the most obvious example of this is Kristallnacht, but it included various other incidents and pogroms.
• Physical displacement—this included forced emigration, resettlement, expulsion, deportation, and ghettoization to physically displace Jewish individuals and communities.
• Internment—this includes the forcing of Jews into ghettos, concentration camps, and forced-labor camps, where many died from starvation, disease, and other inhumane conditions.
• Widespread theft—throughout the period of 1933 to 1945, Jews' property, personal belongings, and valuables were confiscated as part of the Holocaust.
• Forced labor—Jews were expected to perform forced labor in service of the Axis war effort or for the enrichment of Nazi organizations, either military or commercial.
• Industrialized murder—after 1941, the systematic mass murder of Europe's Jews became a Nazi policy.

The Holocaust is also referred to as the Sho'ah (catastrophe), a term preferred by Israelies, the French, Hebrew speakers, and those who want to be more particular about the Jewish experience during the Holocaust. The term is also preferred by those who are uncomfortable with the religious connotations of the word Holocaust.

Jewish children behind barbed wire fences at a concentration camp.

The word Holocaust comes from the Greek words holos (whole) and kaustos (burned) and was historically used to refer to a sacrificial offering burned on an altar. It came from the Hebrew 'olah, used to refer to a burnt offering to God. Since 1945, the word has been used to refer to the ideological and systematic state-sponsored persecution and murder of European Jews, among the millions of others, by the Nazi German regime between 1933 and 1945.

Considered one of the more horrific terms used by Nazi Germany, Lebensunwertes Leben, or "life unworthy of life," was used to designate human beings whose lives were unimportant according to the regime and therefore, should be killed outright. This term was used to describe the mentally impaired, the "sexually deviant," "enemies of the state" both internal and external, and later the "racially inferior." The thinking encapsulated in this term, used early on by the Nazi regime, would eventually culminate in the construction of the extermination camps.

Medieval painting depicting a Jewish person as a devil.

Nazis did not invent antisemitism. It is an old and widespread prejudice that has taken many forms throughout history, with antisemitism dating back to ancient times in Europe. Prejudices, especially from the Middle Ages on, were largely based on Christian beliefs and thought from the belief that Jews were responsible for the death of Jesus. This resulted in suspicion and discrimination that continued into early modern Europe.

However, as Europe became more secular, and the enlightenment period took hold in the eighteenth and nineteenth centuries, many in Europe tried to move away from religious prejudice and persecution. But the same period resulted in new types of antisemitism, including economic, nationalist, and racial antisemitism. Theories of race, eugenics, and Social Darwinism would be used to justify antisemitism and would largely inform the later version of antisemitism of Nazi Germany.

In 1918, Germany lost the First World War, and right-wing extremists in the country blamed the Jews. They accused the Jews of being capitalist exploiters who profited at the expense of others, and Jews were accused of being followers of communism bent on world domination through revolution. These feelings were influential on the antisemitism that Adolf Hitler laid out in his book, Mein Kampf, and in his later speeches, in which he made no secret of his hatred of the Jews.

Adolf Hitler, with Heinrich Himmler, watching marching columns of soldiers.

The twin goals of racial purity and spatial expansion were at the core of Hitler's worldview. Once the Nazis legally elevated to power over Germany in January 1933, these views would push Nazi domestic and foreign policy. The first official concentration camp opened at Dachau in March 1933, where many of the first residents were political opponents of the Nazi regime, before it would become a killing ground of the Holocaust. In 1933, Jews in Germany were numbered at around 525,000, or around 1 percent of the total German population. But over the next six years, Nazis would undertake an "Aryanization" of Germany, dismissing non-Aryans from civil service, liquidating Jewish-owned businesses, and stripping Jewish lawyers and doctors of their clients.

Part of the Nuremberg identification system.

Also known as the Nürnberg Laws, the Nuremberg Laws of 1935 were new laws to establish the groundwork for a "racial state" announced at a Nazi Party rally in Nuremberg on September 15, 1935. One of the two laws, the Reichsbürgergesetz or Law of the Reich Citizen deprived Jews of German citizenship and designated them as "subjects of the state." The second was the Gesetz zum Schutze des Deutschen Blutes und der Deutschen Ehre or Law for the Protection of German Blood and German Honor, often called the Blutschutzgesetz or Blood Protection Laws. This second law forbade marriage or sexual relations between Jews and "citizens of German or kindred blood." Although Jewish persecution at the hands of the Nazi state apparatus had begun as early as 1933, these laws were seen as the first step in legalizing or formalizing the Holocaust, putting in law what would be motivating factors to the party.

This law held that Jews, defined as a separate race from Germans, could not be full citizens of Germany and therefore held no political rights, while also defining a citizen as any person who is "of German or related blood."

The first of around thirteen ordinances elaborating these laws, the supplementary decree of November 14, 1935, worked to define what a "Jewish" person was. Under this supplement, there were three different categories of "Jew":

1. An individual with three or more Jewish grandparents was classified as a full Jew.
2. An individual with two Jewish grandparents was considered a "Mischlinge of the first degree," or a half-Jew. This category was further subdivided into two subgroups: the first-degree Mischlinge who was married to a Jew or members of a Jewish community referred to as a Geltungsjuden and treated as a full jew; and first-degree Mischlinge baptized into the Protestant or Catholic tradition, known simply as Mischlinge, which removed rights from this individual.
3. An individual with a Jewish grandparent was considered a Mischlinge of the second degree, or a quarter-Jew, and was permitted (at first) to keep their German citizenship. Later decrees would remove more of these rights.

German passport bearing the red "J" denoting a person of Jewish faith.

This was a law against what the Nazis viewed as "race-mixing" or "race defilement," which banned future intermarriages and sexual relations between Jews and people "of German or related blood." These types of relations would lead to "mixed race" children, which, according to Nazi ideology, would undermine the purity of the German race and therefore were considered dangerous. These laws further outlawed Jews from flying the Reich flag or the national German flag and went as far as displaying Reich colors. They further defined the jail terms any person breaking these laws would face.

In part due to the lack of definition in the Nuremberg Laws of 1935, the Nazi government spent time further clarifying the laws. As part of the clarification, they extended the application of these laws to further peoples, such as Roma people, Black people, and descendants of these groups. By extending these laws, other minority groups were "legally" able to be treated and discriminated against as the Jews were in Germany. Further, these laws led to other anti-Jewish laws and decrees that further dehumanized and discriminated against the Jews. The following are examples of these other laws and decrees:

• The Law on the Alteration of Family and Personal Names (August 1938)
• The Decree on Passports of Jews (October 1938)
• The Police Regulation on the Marking of Jews (September 1941)

Image of the gathered representatives at the Evian conference.

With reports coming out of Germany around the maltreatment of Jews and the laws being published, there were growing amounts of Jewish refugees fleeing Germany only to find many of the countries they attempted to flee to, such as Belgium, France, Czechoslovakia, the United States, the United Kingdom, Palestine, or Canada, were unable or unwilling to accept these refugees. Hannah Arendt, speaking on the Jewish refugees' predicament, described:

[The refugees] were welcomed nowhere and could be assimilated nowhere. Once they had left their homeland they remained homeless, once they had left their state they remained stateless; once they had been deprived of their human rights they were rightless, the scum of the earth.

The resulting refugee crisis created a political dilemma for many nations, including the United States. President Franklin D. Roosevelt called for the congress to take place in Evian, France in 1938, to have the nations discuss and find a solution to the refugee crisis. The conference included delegates from thirty-two nations, representatives from dozens of relief organizations and related groups, and hundreds of reporters.

Jewish refugees boarding the St. Louis en route to Cuba. They would be forced to return to Europe in 1939.

At the conference, each delegate was said to formally express sorrow over the growing refugee crisis, would boast of their respective nation's hospitality, and then lamented they would be unable to do more to help the growing crisis. The only country to accept more refugees to help the crisis was the Dominican Republic. And each other country had their nation-specific reasons for being unable to accept more refugees.

Responding to the Evian Conference, the Nazi German government was able to state how "astounding" it was that foreign countries criticized Germany for their treatment of the Jews, but none of them wanted to open the doors to them. Efforts were made by some Americans to rescue children, in the form of the Wagner-Rogers Bill, which sought to admit 20,000 Jewish refugee children; it would not be supported by the Senate in 1939 and again in 1940. Widespread racial prejudices among Americans would play a part in the failure to admit more refugees.

German citizens inspecting a destroyed Jewish business the morning after Kristallnacht.

On November 9 to 10, 1938, Nazi leaders and party members unleashed a series of pogroms across Germany against the Jewish population of Germany and recently incorporated territories, and these events would come to be called Kristallnacht or "the Night of Broken Glass." This name was given to the event because of the shattered glass that littered the streets after the vandalism of Jewish-owned businesses, synagogues, and homes. The violent events took place throughout Germany, annexed Austria, and in areas of the Sudetenland in Czechoslovakia recently occupied by Nazi Germany.

People in the act of destroying Jewish businesses.

The violence of Kristallnacht was purportedly due to the death of German embassy official Ernst vom Rath, who had been stationed in Paris. Vom Rath was shot by seventeen-year-old Polish Jew Herschel Grynszpan on November 7, 1938, a few days after German authorities had expelled thousands of Jews of Polish citizenship from living in Germany, causing deportations from Germany—including Grynszpan's parents. This was the apparent motive for revenge that led to the shooting of vom Rath on November 7, and his eventual death on November 8.

Propaganda minister Joseph Goebbels, considered the instigator of Kristallnacht, suggested the Nazi "old guard" should be prepared to demonstrate against the violence. Despite the spontaneous eruption of violence, including mobs of Nazi SA men roaming the streets in cities such as Berlin and Vienna, attacking Jews in their houses, and forcing them to perform acts of humiliation, orders were given to the different police services across Germany that those participants of the pogrom should be left alone, while the Jews should be jailed, Jewish property should be destroyed, and no one should endanger non-Jewish German life or property.

A synagogue burning during the night of Kristallnacht.

The forty-eight hours of violence saw hundreds of synagogues destroyed or burned, Jewish religious artifacts destroyed, Jewish businesses destroyed, and Jewish people beaten, humiliated, jailed, and killed. Approximately 7,500 Jewish-owned businesses, homes, and schools were plundered, around 91 Jews were murdered, and 30,000 were arrested and sent to concentration camps. Nazi officials would claim the Jews themselves were to blame for the riots and would fine the German Jewish community one billion reichsmarks, the equivalent of $400 USD at 1938 rates.

Citizens walking by the destruction of Kristallnacht.

For many, the violence of Kristallnacht, while horrifying in itself, was a message that Nazi antisemitism was not a temporary predicament and would only intensify. From this point forward, measures against German Jews and Jews in captured territories would be more violent and aggressive in nature by the Nazis and their collaborators. By the end of 1938, Jews were prohibited from schools and most public places in Germany and conditions would worsen as the war progressed.

When Hitler began his march of conquest in 1939, with the conquering of Poland and the declaration of war, Nazi Germany began to grow and more European Jews fell under the heel of the fascist regime. The expansion of Nazi Germany into new territories further exacerbated the Jewish persecution, signaling the launch of the ghettos East of Germany and where many Jews further west would later be transported to with the later development of the Nazi camp systems.

Example of a sign forbidding Jews to go passed a checkpoint.

With the expansion of Nazi Germany into neighboring territories, including Poland, Austria, Czechoslovakia, and France, officials began to order the creation of ghettos to isolate the Jews in cities including Frankfurt, Rome, and Prague. The ghettos isolated the Jews from the non-Jewish population, and often there were enclosed districts further isolating the Jews. The Germans established at least 1,143 ghettos in the occupied eastern territories. There were three types of ghettos:

• Closed ghettos—these were often situated in German-occupied Poland and were typified by walls or fences with barbed wire closing access to the ghetto. The German authorities compelled Jews living in the surrounding areas to move into the closed ghetto, exacerbating the crowded and unsanitary conditions. Starvation, chronic shortages, severe winter weather, inadequate and unheated housing, and the absence of adequate municipal services led to outbreaks of epidemics and a high mortality rate. These were the most common type of ghetto.
• Open ghettos—these ghettos tended to have no walls or fences, but there were restrictions for entering and leaving. These existed in German-occupied Poland and occupied Soviet Union, as well as in Transnistria, the province of Ukraine occupied and administered by Romanian authorities.
• Destruction ghettos—these were tightly sealed off and existed for between two and six weeks before the Germans with their collaborators deported or shot the Jewish population concentrated in them. These existed in German-occupied Soviet Union (especially in Lithuania and Ukraine) and Hungary.

A wall being erected to cut of a Jewish ghetto from the rest of a city.

German authorities established the first ghetto in occupied Poland in Piortrkow Trybunalski in October 1939, although the largest ghetto in occupied Poland was the Warsaw ghetto. The Germans ordered Jews in the ghettos to wear identifying badges or armbands, and they required Jews to carry out forced labor for the German Reich. Nazi-appointed Jewish councils, called "Judenraete," administered daily life in the ghettos, and a ghetto police force enforced orders from German authorities and the ordinances of the Jewish councils. This included facilitating deportations to killing centers.

The Warsaw ghetto burning after an uprising of those detained there.

In many places, ghettoization lasted a short time. Some ghettos existed for only a few days, while others lasted for months or years. They were often seen as a provisional measure to control and segregate Jews while the Nazi leadership in Berlin deliberated upon options for the removal of the Jewish population. Jews responded with a variety of resistance efforts, smuggling food, medicine, weapons, or intelligence across the ghetto walls, with or without the involvement or sanction of the Jewish councils. These included violent revolts in Vilna, Bialystok, Czetochowa, and several smaller ghettos.

Crowds of European Jews being herded towards rail cars.

Part of daily life in the ghettos was related to anxiety around deportation to concentration camps and the struggle to find food. In many of the ghettos, the population was isolated from the surrounding city, and the rations supplied by the Germans were subpar, starting the long campaign of starvation that would come to be identified with the Holocaust.

People carrying their valuables onto the cramped trains for deportation.

It has generally been accepted that the Nazis attempted to disguise the deportations of the Jews, often referring to them as resettlements to the East. In this process, inhabitants of the ghettos would be rounded up and made to prepare for their "resettlement," taking only a few valuable possessions. Freight and passenger trains were used for deportations, and in the trains, the prisoners would be sealed inside with little to no room to sit or lie down. No water or food was provided on the trains, which would be intensely hot during the summer and freezing cold during the winter, and the only sanitary facilities were often a single bucket. These journeys could last for days up to weeks. Many packed into the trains would die during the journey, through starvation or overcrowding.

Jewish deportees at the Drancy transit camp near Paris, France, in 1942.

Example of the insignia Jewish people were expected to wear to identify themselves through Nazi occupied Europe.

A part of the ghetto experience was the use of insignia, introduced by the German authorities at the end of 1939, to distinguish Jews by wearing identifying badges. The suggestion started with the Kristallnacht pogrom, when it was suggested Jews should begin to wear identifying badges. This was another part of Nazi Germany's policy aimed at dehumanizing and isolating European Jews. It also allowed for the easier facilitation of their separation from society and subsequent ghettoization. Those who refused or failed to wear the badge would risk severe punishment, including death.

In June 1941, Germany launched Operation Barbarossa, the invasion of once-ally Soviet Union, which Hitler considered Nazi Germany's ideological enemy. As the army moved to invade, commanders were notified that war crimes would not be punished. Behind the German military lines, the Einsatzgruppen moved. These were units designed and charged with the task of killing communist officials, partisans, and Jewish men between the ages of fifteen and sixty. Their actions were officially intended to prevent resistance, but the Einsatzgruppen frequently also killed old people, women, and children.

Soldiers of an Einsatzgruppen unit shoot victims in a ditch.

These special action groups were often referred to as "mobile killing squads" and were best known for their role in the systematic murder of Jews in mass shooting operations as the German army pushed deep into the Soviet territory. The Einsatzgruppen would march behind the German army, and they would seize important sites and prevent sabotage; they would work to recruit collaborators, establish intelligence networks, and identify and neutralize potential enemies. More than anything, they were in charge of rounding up Jewish community members. These community members would be marched to either a previously dug mass grave or (more often) march to a remote location where the Jews would be forced to undress, hand over all of their belongings, dig a mass grave, and then be shot.

Einsatzgruppen member prepares to shoot Jewish man. Below is a pit of the previously murdered.

The Einsatzgruppen did not act alone, and in many territories, they were helped by the German Army and local collaborators. Depending on the area, these collaborators would either participate in the murder, but more often they would help identify Jews or other enemies and assist in security roles. The Einsatzgruppen and their collaborators were able, in the first week of July 1941, in the capture of the cities of Riga and Daugavpils, were able to identify, detain, and murder 5000 Jews. At other points, such as the occupation of Vilnius on June 30, 1941, Einsatzgruppe B were shooting 500 Jews a day.

The mass shootings would prove resource intensive. They required many shooters, escort guards, guns, ammunition, and transport. There were concerns about the inefficiency of the shootings, and the psychological impact on the shooters. The shooting of women and small children would prove to be a great psychological hardship for some SS (Schutzstaffel) men and German policemen. This would lead to the Nazis to begin using mobile gas chambers in the form of modified trucks. However, the trucks proved difficult, as the Jews would be packed into the vans that would be run until the victims were asphyxiated while they were brought to a mass grave where Einsatzgruppen personnel were required to remove bodies and clean the compartments. This would lead to further developments. But at the time, somewhere between 1.5 to more than 2 million victims died in mass shootings or gas vans in soviet territories.

A mobile "gas van" for killing, being inspected by officers.

A German in military uniform shoots a Jewish woman in a mass execution in October 1942.

Historians disagree about the moment when Hitler decided all European Jews should be killed. Although violence had occurred, and there had been plenty of murder in the East, until the second half of 1941, the policy had been as much to make life unbearable for European Jews in the hope of forcing them to emigrate, as it had been to kill them. A signed order for the change in policy does not exist, unlike almost any other decision of Nazi Germany. But it is believed the policy began to change in the second half of 1941. And, on January 20, 1942, during the Wannsee Conference, Nazi officials discussed the planned murder of European Jews.

Heinrich Himmler, one of the architects of the "final solution"

Endlosung der Judenfrage (The Final Solution to the Jewish Question) was a euphemism used by Nazi leaders to refer to the change in policies from that of encouraging or forcing Jews to leave the German Reich to mass murder of European Jews. This period is often considered the last stage of the Holocaust, taking place from 1941 to 1945, and is the period in which the vast majority of Jewish victims were killed. The Final Solution has since been used as a synonym for Nazi Germany's genocidal campaign.

Previous to the Wannsee conference, Hermann Göring, writing under instructions from Hitler, had ordered Reinhard Heydrich, SS general, and Heinrich Himmler's number-two, to submit a general plan of the administrative, material, and financial measures necessary to carry out the genocidal campaign. Heydrich met with Adolf Eichmann, chief of the Central Office of Jewish Emigration, and fifteen other officials from Nazi ministries at the suburb of Berlin, Wannsee. The meeting agenda was focused on devising a plan that would render a "final solution to the Jewish question," with various proposals discussed. These included mass sterilization and deportation to the island of Madagascar, and Heydrich proposed transporting Jews from across Europe to concentration camps in Poland, where they could be worked to death.

Jewish people arrive at the Chelmno extermination camp.

The word "extermination" was never uttered during the meeting, but the implication of these plans was clear. Despite objections to Heydrich's plan—which included the belief it would be time-consuming, with how long it would take for Jews to die, and the question of what would be done to the millions of Jews already in Poland—a few months later, the Einsatzgruppen were marching through eastern Europe, and gas vans in Chelmno, Poland were being used to kill 1,000 people a day. Following that, the killing centers in Poland were established. At first, Belzec, Sobibor, and Treblinka, before the Majdanek camp would be included, and one of the most famous, the Auschwitz-Birkenau (Auschwitz II) camp, would be established with the sole purpose of murdering Jews.

Between 1933 and 1945, if the ghettos are included, Nazi Germany and its allies established more than 44,000 camps and other incarceration camps. These sites were used for a range of purposes, including forced labor, detention of people, and mass murder. These camps are often known as concentration camps, but generally took a few different forms:

• Concentration camps: These were for the detention of civilians seen as real or perceived "enemies of the Reich."
• Forced-labor camps: In these camps, the Nazi regime exploited the labor of prisoners for economic gain and to meet labor shortages. Prisoners here lacked proper equipment, clothing, nourishment, and rest.
• Transit camp: Transit camps served as temporary holding facilities for Jews awaiting deportation. Often these were the last stop before deportations to a killing center.
• Prisoner-of-warp camps: These were primarily used for Allied prisoners of war, including Poles and Soviet soldiers.
• Killing centers: These were established primarily or exclusively for the systematic murder of large numbers of people upon arrival to the site. There were five killing centers for the murder of primarily of Jews.

Prisoners performing slave labor at a concentration camp.

The concentration camps (konzentrationslager) of Nazi Germany were considered an integral feature of the regime, with the first opening in March of 1933, a few months after their rise to power. Many of the camps never closed but were liberated later by the Soviet Union, United States, and United Kingdom as they raced through Germany to reach Berlin and end the European war. These camps were used to detain or confine people, usually under harsh conditions and without regard to legal norms of arrest and imprisonment found in constitutional democracies.

Prisoners performing the Nazi German salute at a concentration camp.

The German authorities established camps across Germany on a near ad hoc basis to handle the masses of people arrested as alleged subversives or "enemies of the Reich." These included camps in Oranienburg, north of Berlin; Esterwegen, near Hamburg; Dachau, northwest of Munich; and Lichtenburg, in Saxony. In July 1934, following the Rohm purge, Hitler authorized SS leader Heinrich Himmler to centralize the administration of the concentration camps and formalize them into a system. To achieve this, Himmler appointed SS Lieutenant General Theodor Eicke as Inspector of Concentration Camps. By the end of 1934, the SS was nominated as the only agency authorized to establish and manage facilities called concentration camps.

Concentration camps are often compared with prisons in modern society, but unlike prisons, concentration camps were independent of any judicial reviews. Nazi concentration camps, instead, were used to serve three main purposes:

• To incarcerate people whom the Nazi regime perceived to be a security threat, and these people were often incarcerated for indefinite amounts of time
• To eliminate individuals and small, targeted groups of individuals by murder, away from the public and judicial review
• To exploit forced labor of the prisoner population, which would grow later out of labor shortages across Germany

Fences and guard towers at a concentration camp.

After Nazi Germany began its expansion east, sparking the beginning of the Second World War, which led to larger groups of potential prisoners and a rapid expansion of the concentration camp system to the east. The central function of the concentration camps did not change, but with the change of Nazi's goals in the east, these camps also permitted the SS to expand the functions of the camps. These camps increasingly became sites where the SS could kill targeted groups of real or perceived enemies of Nazi Germany, and they came to serve as holding centers for pools of forced laborers. However, despite the need for labor, the SS authorities deliberately undernourished and mistreated prisoners in the camps, which resulted in high mortality rates.

The gates at Auschwitz.

One of the specialized types of concentration camps was the extermination camp (vernichtungslager). As their name implied, these camps were used for a singular purpose: the mass annihilation of unwanted persons in the Third Reich and conquered territories. The vast majority of the victims of these camps were Jews, but also included Roma, Slavs, homosexuals, and alleged mental defectives. The major camps of this type were located in German-occupied Poland and included Auschwitz, Belzec, Chelmno, Majdanek, Sobibor, and Treblinka. Prisoners who were deemed able-bodied were used in forced-labor battalions or in tasks of the camps until they were worked virtually to death and then exterminated. These camps were developed due to the difficulties the Einsatzgruppen encountered during their campaign of mass murder and the disquiet these units created in the local populations. They represented a reverse in the process, where the victims were transported to stationary killing centers, rather than bring the killing centers to the prisoners.

Luggage from Jewish victims piled up at an extermination camp.

These camps also offered the efficiency the Nazi Regime was looking for. For example, the staff of Treblinka was only 120, with 20 to 30 personnel belonging to the SS, and the other extermination camps were similar in number. And killing at the centers was done with poison gas. Chelmno, the first of the extermination camps, began gassing prisoners on December 8, 1941. The camp employed gas vans with carbon-monoxide exhaust to asphyxiate prisoners. Auschwitz, the largest and most lethal of the camps, used Zyklon-B.

A pile of bones and debris from a single day's killing at Buchenwald.

Majdanek and Auschwitz were also slave labor camps, while other extermination camps, such as Treblinka, Belzec, and Sobibor, were devoted to killing. At Auschwitz, the Nazis murdered between 1.1 and 1.3 million people and at Treblinka around 750,000 to 900,000 were murdered. Meanwhile, the killing-specific Belzec murdered at least 500,000 people during a ten-month operation period. Most of the extermination camps were closed beginning in 1943 as the ghettos of Poland were emptied of Jews and as the war turned against Nazi Germany. However, Auschwitz continued to receive victims from throughout Europe until Soviet troops approached in January 1945.

Prisoners arriving at Auschwitz for the selection process.

At the extermination camps, a selection process would occur, as Nazi guards would use prisoners to generally maintain the camps, including the emptying of the gas chambers and burning of the bodies. Once the trains arrived at an extermination center, the guards would order prisoners out, in a process in which men were separated from women and children, and an SS physician would examine the deportees to determine their general health.

Women prisoners with heads shaved wearing camp uniforms.

Those deemed fit to work, typically over the age of fourteen or sixteen, would be sent for registration where they were stripped of their clothes and valuables, completely shaved of all of their hair, disinfected and showered, and tattooed with a registration number. They would then receive a striped uniform, hat, and clogs and be forced to work.

Those deemed unfit to work would often include children under the age of sixteen (later brought down to fourteen years in 1944), pregnant women, the handicapped (physically or mentally), the elderly, and the sick. These prisoners would be sent to the gas chambers; though they were, at the time, told they were being sent to showers to clean themselves of grime and lice. Before the gas chamber, the victims were forced to remove all items of clothing and valuables before the shower.

Examples of prisoners' tattoos at Auschwitz.

During the Holocaust, concentration camp prisoners received tattoos for registration at Auschwitz. The Auschwitz concentration camp complex consisted of Auschwitz I, Auschwitz II (Auchswitz-Birkenau), and Auschwitz III (Monowitz and subcamps). Incoming prisoners were assigned a camp serial number which, initially, was sewn onto their uniform. Only prisoners selected for work were tattooed. Those sent directly to the gas chambers were never registered.

The first people to be tattooed were Soviet prisoners. These prisoners were initially stamped by a special metal stamp made of interchangeable numbers made of needles approximately one centimeter in length. This allowed a serial number to be punched in a prisoner's chest, and ink was rubbed into the bleeding wound. This was an impractical method, and a single needle method was introduced. The tattoo location was also changed, moving to the inner side of the left upper forearm. Separate series of numbers were introduced based on prisoner categories (Soviet POWs, Hungarian Jews, Polish Jews, reeducation prisoners, and more), and German prisoners in the camp were never tattooed.

Between 1939 and 1945, there were at least seventy medical research projects undertaken by Nazi Germany, which often involved cruel and lethal experimentation on human subjects. Many of these experiments were undertaken at the concentration and extermination camps, where the constant supply of new victims gave researchers a near-constant supply of research subjects. At least seven thousand victims of such medical experiments have been documented, with victims including Jews, Poles, Roma, political prisoners, Soviet prisoners of war, homosexuals, and Catholic priests. These experiments tended to fall into three general areas:

• Research aimed at improving the survival and rescue of German troops
• Testing of medical procedures and pharmaceuticals
• Experiments that sought to confirm Nazi racial ideology

A picture of a victim of Nazi medical experimentation showing a phosphorus burn.

Many experiments in the camps intended to facilitate the survival of military personnel in the field. For example, at Dachau, physicians conducted high-altitude experiments on prisoners to determine the maximum altitude from which crews of damaged aircraft could parachute to safety. Other experiments at Dachau included so-called freezing experiments on prisoners to find treatments for hypothermia, and various tests to make seawater drinkable.

A victim of Nazi medical experiments.

Experiments were undertaken to develop and test drugs and treatment methods for injuries and illnesses that German military and occupation personnel encountered. At the German concentration camps of Sachsenhausen, Dachau, Natzweiler, Buchenwald, and Neuengamme, scientists tested immunizations for compounds and antibodies to prevent and treat contagious diseases, such as malaria, typhus, tuberculosis, typhoid fever, yellow fever, and infectious hepatitis. Other experiments included those into bone-grafting, amputations, and possible antidotes to phosgene and mustard gas.

Photographs of twins used in Nazi medical experiments.

The third major category of experimentation undertaken at the camps by Nazi scientists sought to advance the racial and ideological tenets of the Nazi worldview. The most infamous of these were the experiments of SS physician Josef Mengele, who conducted inhumane medical experiments on prisoners at Auschwitz. Some of his most well-known studies of Mengle were on twins, and most of his experiments caused great harm or death to the prisoners. Other Mengele experiments were on the Roma people, similar to experiments undertaken by Werner Fischer at Sachsenhausen, which aimed to understand how different "races" withstood various diseases.

Research undertaken by August Hirt at Strasbourg University joined this, as he intended to establish "Jewish racial inferiority" with a scientific basis. Other experiments included investigating methods of efficient and inexpensive procedures for mass sterilization for those considered to be racially or genetically undesirable.

Portrait of Joseph Mengele.

Josef Mengele, born on March 16, 1911, earned a PhD in physical anthropology from the University of Munich and held a doctoral degree in genetic medicine. He joined the Nazi Party in 1937 and was drafted into the army in June 1940, where he volunteered for the medical service of the Waffen-SS. While little is known about his time between his drafting in 1940 and 1943, what is known is that he received a promotion to the rank of SS captain in 1943 and transferred to Auschwitz on May 30, 1943.

At Auschwitz, Mengele took a position at Chief Camp Physician and worked with approximately thirty other physicians. During the selection process, these physicians would pick possible subjects for their experimentation. He was known, for his behavior during the selection process, as the "Angel of Death" or sometimes the "White Angel" and would be closely associated with the selection duty.

Twin subjects of Mengele's experimentation at Auschwitz.

He was often at the selection process even during his off time while searching for twins. His interest in twins was based, in part, on twin research that had been popular during the 1930s as an ideal tool in weighing the factors of human hereditary and environment. While during the 1930s Mengele and his mentor had performed legitimate research using twins as test subjects, at Auschwitz he had full license to maim and kill his subjects, and he performed a wide range of agonizing and often lethal experiments with Jewish and Roma twins.

He had other research interests, including a fascination with heterochromia, a condition in which the irises of an individual differ in coloration. Mengele collected the eyes of many of his murdered victims at Auschwitz, in part to furnish what he would call research materials to colleagues interested in eye pigmentation. And he conducted experiments into attempts to artificially change eye color. He also documented in camp inmates the progression of the disease Noma, a type of gangre that destroys the mucous membrane of the mouth and related tissues.

Mengele would escape the Allies and persecution for his crimes. He would later be discovered in Brazil, after it had been determined he had moved to South America, first to Paraguay. In Brazil, he had met up with another Nazi party member, Wolfgang Gerhard, and in 1985 it was determined a man named Gerhard who had died of a stroke in 1979 was actually Mengele, who had assumed Gerhard's identity.

Following the medical experimentation, mass sterilization, and the subsequent trials that discovered more about these camp experiments, the Nurmeberg Code was developed to address abuses committed by medical professionals during the Holocaust. The Nuremberg Code included the principle of informed consent and created standards for scientific experimentation and research. The Code served as a blueprint for the principles that ensure the rights of subjects in medical research and to lay out a basis for medical ethics. However, due to where the Codes originated (the horrors of the Holocaust), their applicability to modern medical research has been debated, in part due to the lack of a democratic framework to the development of the Codes. However, the ten principles of them have in many places informed the rights of patients and medical subjects in law. These ten principles include:

1. The voluntary consent of the human subject is absolutely essential
2. The experiment should be such as to yield fruitful results for the good of society, unprocurable by other methods or means of study, and not random and unnecessary in nature
3. The experiment should be so designed and based on the results of animal experimentation and a knowledge of the natural history of the disease or other problem under study that the anticipated results justify the performance of the experiment
4. The experiment should be so conducted as to avoid all unnecessary physical and mental suffering and injury
5. No experiment should be conducted where there is an a priori reason to believe that death or disabling injury will occur
6. The degree of risk to be taken should never exceed that determined by the humanitarian importance of the problem to be solved by the experiment
7. Proper preparations should be made and adequate facilities provided to protect the experimental subject against even remote possibilities of injury, disability, or death
8. The experiment should be conducted only by scientifically qualified persons
9. During the course of the experiment the human subject should be at liberty to bring the experiment to an end if he has reached the physical or mental state where continuation of the experiment seems to him to be impossible
10. During the course of the experiment, the scientist in charge must be prepared to terminate the experiment at any stage, if he has probable cause to believe, in the exercise of the good faith, superior skill, and careful judgment required of him, that a continuation of the experiment is likely to result in injury, disability, or death to the subject

A photograph taken of a forced march of Jewish prisoners through a small town.

In early 1945, Nazi Germany was on the verge of military defeat. Allied forces approached the Nazi camps, and the SS, attempting to finish the job they started and to hide their crimes, organized forced evacuations that came to be called "death marches" of concentration camp inmates. This was partially in response to the Soviety offensive of the year prior, in which they had discovered the first major Nazi concentration camps, Majdanek. Following this, Himmler ordered that prisoners from all concentration camps and subcamps be forcibly evacuated toward the interior of Germany. The evacuation has been suggested to have had three major purposes:

• SS authorities did not want prisoners to fall into enemy hands alive to tell their stories
• The SS thought they needed prisoners to maintain the production of armaments
• Some SS leaders, including Himmler, believed they could use Jewish prisoners as hostages to bargain for a separate peace in the west and guarantee the survival of the Nazi regime

Prisoners seen on a "death march"

In the early parts of 1944, most evacuations were undertaken by train, or, in some positions, by ship. But as winter approached, and the Allies encroached on the German territory, SS authorities increasingly resorted to evacuations on foot. The SS guards had orders to kill prisoners no longer capable of walking or traveling, and as the evacuations took place on foot during the winter of 1944-1945, the number who died of exhaustion and exposure during the routes increased. Further, during the marches, SS guards would mistreat prisoners, and any prisoner who collapsed or could not keep pace would be shot. One survivor of the marches recalled

No food had touched my lips all day before. Others "snatched" whatever they could - grass, snails, potatoes left in the fields - but my throat was blocked, although my stomach was growling with hunger. I had nothing else, so I ate snow. My whole body shook with cold... The march went on for days and nights and nobody knew where we were being taken. If they want to mow us down somewhere with machine guns, why don't they do it immediately? Or, perhaps there are special installations for that? Perhaps they are taking us again to some new installations for killing by gas? But it seemed that there was no need for any of that; at least two-thirds of the prisoners were already lying lifeless by the roadside. In a few days all of us would suffer the same fate.

The prisoner evacuations were chaotic. Once they left a camp, the columns of prisoners were under control of the German guards, but the guards were often disorganized and brought with them little food or supplies. Often, faced with the chaos at the end of the war, they murdered their prisoners. Other times, the Allies would come across the columns and rescue the prisoners, while local Germans also came face-to-face with the prisoner being marched through their towns.

Soviet soldiers and emaciated prisoners at the liberation of Auschwitz.

One of the most unexpected discoveries for the Allies as they marched towards Berlin was the discovery of the concentration camps. There, they confronted the worst crimes of the Nazi regime and the horrible conditions of the prisoners. The first camp to be liberated was Majdanek, located in Lublin, Poland, liberated by the Soviet army as they advanced westward. From this liberation came the first images and news of the camps presented to the Western media. Here, the Soviet army found prisoners who had been left at Majdanek, mostly Soviet prisoners of war, and encountered the first pieces of evidence of the mass murder committed at the camp. Six months later, the Soviets would liberate Auschwitz, where they found more than six thousand emaciated prisoners alive.

The crematoria at the liberation of the Majdanek camp.

As the allies continued to liberate concentration camps, they continued to find apalling scenes. For example, Bergen-Belsen, liberated by British forces in April 1945, had become exceptionally overcrowded and thousands of unburied bodies were strewn about the camps, while the barracks were overfull of around 60,000 starving and mortally ill prisoners, around 60 percent of whom suffered from typhus. In many cases, when coming upon the camps, the troops, physicians, and relief workers would try to provide nourishment to the prisoners, but many were too weak to digest food and could not be saved. And, in some cases, the prisoners would eat themselves to death. Half of the prisoners discovered at Auschwitz would die within days of being freed. And the prisoners themselves often struggled with guilt for having survived, while also looking forward to being free, and some felt overwhelmed. As survivor and psychiatrist Viktor Frankl expressed,

Timidly, we looked around and glanced at each other questioningly. Then we ventured a few steps out of the camp. This time no orders were shouted at us, nor was there any need to duck quickly to avoid a blow or a kick. 'Freedom,' we repated to ourselves, and yet we could not grasp it.

American soldiers reacting to the discovery of a railcar loaded with dead found near Dachau concentration camp.

The 42nd "Rainbow" Division rolled into the Bavarian twon of Dachau in their march to Berlin, where they expected to discover either an SS training facility or a prisoner-of-war camp. Instead, they discovered piles of emaciated corpses, dozens of train cars filled with decomposed human remains, and thousands of "walking skeletons" who had survived Dachau. The concentration camp in the Dachau complex was composed of 32 squalid barracks surrounded by an electrified barbed-wire fence, a ditch, and seven guard towers. Prisoners here were subject to medical experiments, including injections of malaria and tuberculosis, untold thousands that died from hard labor or torture, and the on-site crematorium which routinely burned the corpses. Forged into the gates separating the concentration camp from the rest of Dachau were the words Arbreit Macht Frei or "Work sets you free."

Bodies piled up outside of the Dachau crematoria.

What the soldiers found at Dachau, and what the 45th "Thunderbird" Division discovered on the death train, was scarring for these soldiers. The 45th division had been in combat for 500 days and thought they had witnessed every atrocity of war, but the train filled with innocent decaying bodies was more than many could take. Soldiers broke down in sobs. And others tried to find those responsible, including murdering German officers that had surrendered to them.

American soldiers inspecting an overstuffed oven of a crematorium at an extermination camp.

Inside Dachau, it got worse. The American GIs liberating the camp reportedly rounded up the staff and SS officers inside the camp and lined them up to gun them down out of anger and revulsion. The American GIs stayed for days before moving on. The care of the prisoners was entrusted to combat medical units, while word of what happened at places like Dachau and Buchenwald spread through the Allied ranks. Despite previous camps liberated on the eastern front in 1944, there was distrust of the Soviet discoveries on the western front, as there was a general distrust for the Soviets themselves.

German citizens and SS women remove bodies of victims from concentration camp at Belsen, supervised by British soldiers.

Prisoners at the Dachau concentration camp cheer American soldiers.

Often the end of the Holocaust is suggested as May 1945. By this time, the majority of the Nazi camps were either liquidated or liberated. The Nazi Regime in Germany had fallen. And the world was learning about the horrors of the Holocaust. The "death marches" had been a terrible final chapter of the Holocaust where many more Jews died and were left at the side of the road.

With the liberation and the fall of Nazi Germany, any policy of extermination to the European Jews was ended; however, that did not mark the end of the suffering for many of the survivors. Hundreds of thousands of Jews who had survived, either in the camps, in hiding, or in other countries, returned to their homes. They were often met with anger and animosity, found their homes occupied by others, and in some cases would flee further westward. Antisemitic gangs in places such as Poland killed Jewish survivors on their return home, with some estimating around 1,500 Jewish survivors dying in Poland alone in the months after liberation.

American soldiers speak to German civilians amid a pile of Holocaust victims, ensuring the civilians were aware of the crimes.

Many survivors of the Holocaust tried to reach Eretz Israel, but the British authorities deported them to detention camps in Cyprus until the State of Israel was established, when there was a mass immigration of survivors of the Holocaust. Approximately 100,000 Jewish displaced persons immigrated to the United States, Canada, Australia, and Latin American countries.

The Nuremberg Trials took place from 1945 to 1946, as an attempt to seek justice for the crimes of the Nazi regime. Former Nazi members were indicted and tried as war criminals by the International Military Tribunal. These trials were for more than the crimes of the Holocaust, and included the following:

• Crimes against peace (planning, initiating, and waging of wars of aggression in violation of international treaties and agreements)
• Crimes against humanity (exterminations, deportations, and genocide)
• War crimes (violation of the laws of war)
• "A common plan or conspiracy to commit" the criminal acts in the first three counts

Defendants at the Nuremberg trial.

The authority of the International Military Tribunal to conduct these trials came from the London Agreement of August 8, 1945, when representatives from the United States, Great Britain, and Soviet Union, along with the provisional government of France, agreed to a charter for an international military tribunal to conduct trials of major Axis war criminals whose offenses had no particular location.

Defendant on trial at the Nuremberg trial.

As a result of the trials, 199 defendants were tried. Of those, 161 were convicted and 37 were sentenced to death. Crimes of the Holocaust were included in a few of the trials, and defendants generally acknowledged the crimes they were accused of but denied their responsibility. Trials into the crimes of the Holocaust would continue, and investigations would be launched to find many of the Nazi leaders and individuals who had escaped justice, such as Adolf Eichmann and Josef Mengele.

Preceding trials, many of which were held at Nuremberg and are often included in the title of the Nuremberg Trials, included the Doctors Trial, which accused twenty-three defendants of crimes against humanity, including medical experiments on prisoners of war. The Judges Trial charged sixteen lawyers and judges with furthering the Nazi plan for racial purity through eugenics laws. Other trials included those dealing with German industrialists benefitting from the use of slave labor and plundering of occupied countries and SS officers accused of violence against concentration camp inmates.

Image from the Doctors Trial.

The findings at Nuremberg led to the United Nations Genocide Convention of 1948, the Universal Declaration of Human Rights of 1948, and the Geneva Convention on the Laws and Customs of War of 1949. The Trials also served as a precedent for the trials of Japanese war criminals in Tokyo and a precedent for later tribunals for war crimes committed in the former Yugoslavia and in Rwanda.

American soldiers force civilians to walk past rows of Holocaust victims.

One of the enduring questions of the Holocaust is centered around if the world knew of the crimes of the Nazi regime or if they were done in complete secret. The denial of the events of the Holocaust occured as early as the Holocaust, with many citizens near the concentration and extermination camps ignoring the thick smoke pouring into the sky day and night. Or believing the lies of quarantining, resettlement, and evacuation, and the overall use of bureaucratic language to cover up the mass murder.

But the claim of many of the German citizens after the fall of Berlin in 1945 was that they did not know about the camps and their atrocities. However, German newspaper and magazine archives show there were phases of public "desensitization" that exposed citizens to the horrors that would come. But there were no reports of the "final solution," and it is generally accepted that, as much as the German populace may have known something was going on, and that it was not good, they may not have known the specific or precise crimes, in part because they did not ask questions.

The Nazis themselves would go to great lengths to hide their crimes. One such fabrication involved Theresienstadt, a transit camp in the former Czechoslovakia, that the Nazis pretended was a resttlement camp. The International Red Cross demanded to investigate the camp in 1944, based on some reports that had leaked out through the world media. Before they could arrive, the Nazis forced prisoners to plant flowers and decorate the baracks, and the Nazis produced a promotional film of Theresienstadt, in which prisoners were coerced to be cheerful for the camera in exchange for food.

Goebbels on the cover of Time magazine in 1933.

As early as 1941, information regarding the Nazi crimes began to leak out to the international media. This included early sources including German police reports intercepted by British intelligence; local eyewitnesses; escaped Jews reporting to the underground, Soviet, or neutral sources; and Hungarian soldiers on home leave. And in 1942, reports of a Nazi plan to murder all Jews, including details on methods, numbers, and locations, reached Allied and neutral leaders from various sources.

This information resulted in broadcasts by the British Prime Minister Winston Churchill in 1941 summarizing the findings. This was supported by confirmation in spring 1942, when American journalists stranded in Germany were exchanged for Axis nationalists stranded in the United States. In 1942, after a report from occupied Poland confirming the murdering of the Jews, resulted in headlines in The London Times, the Montreal Daily Star, the Los Angeles Times, and the New York Journal American, which remarked on the killing of Jews by Nazi Germany, estimated at the time to be around 1 million. And during this period, Time magazine carried news about the Holocaust as early as 1933, when the magazine commented on Hitler's antismemitic theories.

American's reading papers at a declaration of war.

One difficulty with the reporting was the skepticism on the part of the journalists receiving the secret reports and intelligence reports about the Holocaust and the public reception of this news. American journalists tended to be caustion about claims of mass murder because of related stories that had been reported during World War I that would prove to be false. This often resulted in editors rarely featuring the stories on the front page, and careful not to emphasize claims of atrocities.

Meanwhile, public opinion polls from 1943 showed Americans were skeptical and tended to think the fact that 2 million European Jews had been murderd was a rumor. By 1944, about three-quarters of respondents to these polls believed concentration camps were a part of the Nazi plan, but the polls still showed that the respondents did not understand the number of victims involved. A Gallup poll of 1944 showed that most people who guessed thought the number of victims would be in the hundreds of thousands or less.

It would not be until 1944 that many in the world not directly exposed to the crimes of the Holocaust would begin to accept the truth of what had happened. By 1945, a Gallup poll showed 84 percent of Americans believed the reports of the Holocaust. However, there remained skepticism, and the number of dead continued to be underreported. This led to the decision to distribute photographs that provided the brutal and shocking evidence of the atrocities. These pictures were shown around the world, including to German people, and helped the world's public understand the depth of the horror of the crimes of Nazi Germany.

The question of who was responsible, ultimately a question of justice, also gets at an uncomfortable truth about the Holocaust: many of those who perpetrated the crimes and atrocities would receive little to no punishment. Some would go undiscovered until their death. Many would commit suicide before they could be captured or shortly after incarceration. And when attempting to meter out justice for these crimes, can any just punishment truly do justice to the horrors committed?

Adolf Hitler surrounded by party leaders.

One undoubtable truth about the responsibility for the Holocaust lies at the feet of the Nazi leadership. The genocide was inspired, ordered, approved, and supported by Adolf Hitler, but he did not act alone, nor did he lay out an exact plan. Rather, other Nazi leaders coordinated, planned, and implemented the mass murder, including Hermann Göring, Heinrich Himmler, Reinhard Heydrich, and Adolf Eichmann.

Heinrich Himmler with Adolf Hitler.

Heinrich Himmler was one of the main architects of the Holocaust—the man who set up the system of concentration camps, inspected those camps, and inspired competition amongst the camps to see who could kill more Jews, leading to the use of novel killing methods such as the use of Zyklon-B at Auschwitz. Himmler, like many in the inner circle of the Nazi party, was power-hungry and wanted to rise to be Hitler's second, to inherit the power of the government once Hitler died. To prove his worth, he set up the Einsatzgruppen to help Hitler's plan for German resettlement of Poland, or to "cleanse" the area for those Germans.

In 1933, Himmler had established the first Nazi's concentration camp at Dachau. And in 1941, he would assign General Odilo Globocnik with the implementation of Operation Reinhard, which was the plan for the systematic murder of Jews and included the establishment of the extermination camps.

Heinrich Himmler surrounded by SS members.

Nothing can occur just because leadership decides it should. But, it requires and relies on the institutions and organizations established to help them reach their decision. In the case of the Holocaust, the Nazi regime relied on many of the organizations they had previously established across Germany. These included the SA, also known as "Brownshirts," and were the early Nazi militia; the SS, or Schutzstaffel; the SD, or Sicherheitsdienst, also known as the Gestapo; and the Order Police. All of these organizations played active and deadly roles in the Holocaust.

Hitler, surrounded by the SA or "Brownshirts".

Other organizations that helped included the German military, the German national railway, the German healthcare system, the German civil service, and the German criminal justice system. Besides these systems, many German businesses, insurance companies, and banks were either involved in the Holocaust or benefitted, in some cases from the slave labor, from the Holocaust.

Other participants in the Holocaust across Germany included ordinary Germans. They participated in a variety of ways, with some cheering as Jews were beaten or humiliated, some denouncing Jews for disobeying racist laws and regulations; while others bought, took, or looted their Jewish neighbors' belongings and properties. Many of these individuals had their own motivations, such as enthusiasm, careerism, fear, greed, self-interest, antisemitism, and political ideals.

Leaders of Vichy France.

Nazi Germany was also not alone in perpetrating its crimes. They relied on help from countries allied with Nazi Germany and collaborators. Collaborators are often thought of as the regimes and organizations that cooperated with German authorities in an official or semi-official capacity. The allies and collaborators included the following:

• The European Axis Powers and other collaborationist regimes, such as Vichy France. These governments often passed antisemitic legislation and cooperated with German goals.
• German-backed local bureaucracies, especially local police forces. These organizations helped round up, intern, and deport Jews, even in countries not allied with Germany, such as the Netherlands.
• Local auxiliary units made up of military and police officials and civilians. These German-backed units participated in massacres of Jews in eastern Europe, often voluntarily.

Benito Mussolini riding with Hitler.

The term "allies" and "collaborators" also refer to individuals affiliated with these governments and organizations. Some of the deadliest of these were neighbors, acquaintances, colleagues, and even friends who denounced Jews to Nazi German authorities. How many chose to do this is largely unknown, but often they could reveal Jews' hiding places, unmask false Christian identities, and otherwise identify Jews to Nazi officials. The motivations of these people could be far-ranging, including fear, self-interest, greed, revenge, antisemitism, and political or ideological beliefs.

Some of these individuals directly profited from the Holocaust. They would move into newly vacated homes, take over newly-vacated businesses, and even steal the possessions and valuables of Jews. There was widespread theft and plunder that accompanied the genocide. For some, the inaction and indifference to the crimes of the Nazi government was enough to be considered a collaborator to the Holocaust.

Arguably, the first to deny the Holocaust were the Nazis. Often they used veiled language and secret operations and covered up the murders by destroying any evidence, working to keep the world in the dark of what they were doing, which could have impeded or stopped their goals for the annihilation of European Jews. However, since the event, there have been various attempts by individuals, organizations, and countries to deny that the events of the Holocaust occurred. Some of the worst have suggested that the events of the Holocaust were a myth invented to advance Jewish interests. Often, in this way, Holocaust denial is another form of antisemitism and has been called a second genocide, as it denies the death of the murdered and seeks to erase those victims from history, often called a double-dying.

Often, and unsurprisingly, Holocaust deniers wish to wash away the stain of Nazism in order to make the Nazi ideology an acceptable political alternative. Many organizations that have denied the Holocaust have done it for this reason, such as Harold Covington, leader of the National Socialist White People's Party, who on July 24, 1996, called the Holocaust a Jewish conspiracy used to give the Jews an advantage over everyone else.

One thing Holocaust deniers tend to have to deal with is the mountain of evidence, despite the Nazi's attempts to destroy the evidence, including the Jews themselves. Often, to do this, Holocaust deniers claim the survivors of the Holocaust lied about their experiences, the soldiers liberating the camps exaggerated their experiences, and the films and photos of the atrocities, including those captured from the Nazis, were themselves made up or forged and confessions were coerced. They also tend to deny the existence of the gas chambers and claim these chambers were built by the Allies to make Nazi Germany look bad. Some have gone far enough to argue that the Allied countries should be held responsible for the deaths in the camps. Arguing, in some cases, that their bombing attacks prevented the delivery of supplies and medicines from reaching the camps.