Generally speaking, a concentration camp is a place where people are concentrated and imprisoned without trial. Inmates are usually exploited for their labour and kept under harsh conditions, though this is not always the case.

In Nazi Germany after 1933, and across Nazi controlled Europe between 1938 and 1945, concentration camps became a major way in which the Nazis imposed their control.

Separating concentration camps and extermination camps

It is key to separate concentration camps from extermination camps.

The aim of the Nazi concentration camps was to contain prisoners in one place.  The administration of the camps had a distinct disregard for inmates’ lives and health, and as a result, tens of thousands of people perished within the camps.

The aim of the Nazi extermination camps was to murder and annihilate all races deemed ‘ degenerate ’: primarily Jews but also Roma .

Development of concentration camps

The first concentration camps in Germany were set up as detention centres for so-called ‘enemies of the state’. Initially, these people were primarily political prisoners such as communists , but this soon expanded to also include Jehovah’s Witnesses, homosexuals, Roma, and so called ‘ a-socials ’.

After March 1938, when Germany annexed Austria in an event known as Anschluss  thousands of German and Austrian Jews were arrested and detained in Dachau, Buchenwald and Sachsenhausen concentration camps. The mass detention of Jews on the basis of the Nazis’ racial ideology intensified following Kristallnacht and continued until the end of the Second World War. This imprisonment was an escalation of the Nazis’ previous persecution of Jews.

Imprisonment in the Nazi concentration camps was usually indefinite, and whilst (initially) some people were released in just a few days, most endured weeks, months or years of detention. Sanitation and facilities were extremely poor across all camps. Brutal treatment, torture and humiliation was commonplace.

Inmates in concentration camps were also usually subject to forced labour. Typically, this was long hours of hard physical labour, though this varied across different camps. Many camps worked their prisoners to death.

Approximately one million people died in concentration camps over the course of the Holocaust. This figure does not include those killed at extermination camps.

Extermination camps were used by the Nazis from 1941 to 1945 to murder Jews and, on a smaller scale, Roma .

To implement the ‘ Final Solution ’, the Nazis established six purpose built extermination camps on Polish soil. These were:

1. Chełmno (in operation December 1941-January 1945)
2. Bełżec (in operation March-December 1942)
3. Sobibór (in operation May-July 1942 and October 1942-October 1943
4. Treblinka (in operation July 1942-August 1943)
5. Majdanek (in operation September 1942-July 1944)
6. Auschwitz-Birkenau (in operation March 1942-January 1945)

Chełmno was the first extermination camp to be established in December 1941. Its purpose was to murder the Jews of the surrounding area and the Łódź ghetto. The facility contained three gas vans in which victims were murdered by carbon monoxide poisoning. Once dead, the vans were driven to a nearby forest and the victims were buried in mass graves.

After the Wannsee Conference of 1942, the Nazis built additional extermination camps at Bełżec, Sobibór and Treblinka. These camps were specifically built near railway lines to make transportation easier. Instead of vans, stationary gas chambers, labelled as showers, were built to murder people with carbon monoxide poisoning created using diesel engines.

A concentration camp had been established at Majdanek in 1941. In the spring of 1942, following the Wannsee Conference, the camp was adapted to become an extermination camp by the addition of gas chambers and crematoria.

Auschwitz-Birkenau was a complex, consisting of a concentration camp, a forced labour camp and an extermination camp. Eventually it had a network of more than 40 satellite camps. Following tests in September 1941, the lethal gas Zyklon B was selected as the method of murder. Auschwitz initially had one gas chamber at the Auschwitz I camp, but this was soon expanded. By 1943, four new crematoria, with gas chambers attached, had been built in Auschwitz II. Approximately 1.1 million people were murdered in the Auschwitz gas chambers.

Not everyone who arrived at the extermination camps was murdered on arrival. Some were selected for various work tasks to help the camp operations run smoothly. Jobs included sorting and processing the possessions of everyone who arrived at the camp, administrative work and heavy manual work.

The majority of those selected for any kind of work within this type of camp would die within weeks or months of their arrival from lack of food, disease or overwork. Those that survived were often killed after a short period and replaced with new arrivals.

Over the course of the Holocaust, more than three million people were killed at extermination camps.

Transit camps were camps where prisoners were briefly detained prior to deportation to other Nazi camps.

Following the start of the Second World War, the Nazis occupied a number of countries. Here, they implemented antisemitic and racial policies as they had done in Germany. These policies led to the establishment of a number of transit camps across the different occupied countries. Prisoners were held in these camps prior to their deportation to other camps, such as Bergen-Belsen or Auschwitz.

Overall, the conditions in the transit camps were similar to that of concentration camps – unsanitary and awful. Facilities were poor and overcrowding was common.

Unlike most of the concentration camps within Germany not all of the transit camps were run by the SS . Camps could be run by local collaborators in the countries that they were based, such as Drancy, near Paris in France, which was run by the French Police until 1943.

The Nazis started using forced labour shortly after their rise to power. They established specific Arbeitslager (labour camps) which housed Ostarbeiter (eastern workers), Fremdarbeiter (foreign workers) and other forced labourers who were forcibly rounded up and brought in from the east. These were separate from the SS-run concentration camps, where prisoners were also forced to perform labour.

The use of forced labour first began to grow significantly in 1937, as rearmament caused labour shortages.  Following the outbreak of the Second World War, the use of labour again increased sharply.

The invasion of the Soviet Union in June 1941 further heightened demands on the war economy, and in turn, for labour. At the same time, this invasion brought thousands of potential new workers under Nazi control. These prisoners were called Ostarbeiter (eastern workers) and Fremdarbeiter (foreign workers). The Nazis deported these people to forced labour camps, where they worked to produce supplies for the increasingly strained war economy or in construction efforts.

As in most Nazi camps, conditions in forced labour camps were inadequate. Inmates were only ever seen as temporary, and, in the Nazis view, could always be replaced with others: there was a complete disregard for the health of prisoners. They were subject to insufficiencies of food, equipment, medicine and clothing, whilst working long hours. There was little or no time for rest or breaks. As a result of these conditions, death rates in labour camps were extremely high.

By 1945, more than fourteen million people had been exploited in the network of hundreds of forced labour camps that stretched across the whole of Nazi-occupied Europe.

Allied military officers and personnel who were captured by, or surrendered to, the Nazis were also imprisoned in camps. These camps were called prisoner of war, or POW, camps. Over one thousand prisoner of war camps existed throughout the Third Reich during the Second World War.

The camps held British, American, French, Polish and Soviet military personnel. There were many different types of camps, some held specifically Navy personnel, others held only officers, and others held a more general array of prisoners.

Germany had signed and agreed to the terms of the Geneva Convention of 1929 , which set out the basic treatment of prisoners of war, but these were rarely upheld in full by the Nazis. Conditions inside the camps were usually miserable, with scarce food and poor sanitation widespread. Many of the inmates were also forced to carry out hard labour.

The Nazis believed that Soviet citizens were subhuman and racial enemies due to Soviet communism , which they saw in direct opposition to Nazism. As such, they treated Soviet prisoners of war particularly harshly. Over the course of the war approximately 5.7 million Soviet army members were captured by the Nazis. Over 3.3 million army personnel died at the hands of the Nazis through starvation, disease, lack of facilities or mass shootings.