Which is what makes the idea of "extermination through work" so inane. It's easy to starve somebody to death. It's very difficult to starve somebody almost to death and then maintain them in that state while they are performing manual labor. Even holding a gun to somebody's head isn't going to compensate for the effects of starvation. When the car runs out of gas, slashing its tires won't make it go faster.
Extermination through work in the strict sense was applied only to special categories of largely non-Jewish prisoners handed over by Thierack, the minister of justice, to Himmler in late 1942, for internment in concentration camps.
The term has become a kind of metaphor for the entire slave labour system, but in strict terms this is not entirely accurate. There were quite sharp divisions between labouring and non-labouring prisoners, which on repeated occasions led to the mass extinction of large groups of people, eg in 1941 with the Soviet POWs, and in 1942 with the Jews of the Generalgouvernement.
Before these specific events, rationing had been imposed across occupied Europe, and it is no surprise that Jews came last in the eyes of the Nazis. Thus when they were in ghettos and forced labour camps (not concentration camps), it was hardly unusual to undersupply them for racist reasons, and thus decimate the potential workforce who were often dropping like flies after a few weeks in a badly provisioned forced labour camp. That's what happened in 1940-41 in Poland.
Once the 'surplus' Jews had been exterminated, this left a few hundred thousand labouring Jews interned in camps and increasingly, in concentration camps. In January 1943 there were more Jews working in forced labour camps than concentration camps. By mid-1944, there were virtually no forced labour camps left as they had either been liquidated or transformed into sub-camps of the concentration camp system.
The concentration camps expanded considerably in this period, going from around 100,000 inmates in 1942 to 500,000 inmates in the summer of 1944 and 700,000 by January 1945, including Jews and non-Jews.
In 1940-42, the purpose of the 'classic' camps was to punish political and other opponents, thus deaths were more or less factored in to the equation. From 1942, the concentration camps were harnessed to industrial and other production, which caused huge problems in adjusting the mentality of the prewar generation of camp commandants and other officers. The death toll was reduced in 1943, but deaths were never reduced back down to the small numbers seen before 1939.
It should be no surprise that camp inmates were fed at lower ration scales than ordinary forced labourers, they were close to last on the priority list. If they were fed better, then a spell in a concentration camp would not be punishment for Russian and Polish workers, who together formed a very high proportion of the KZ inmate population by 1943.
The loss of life from malnutrition, maltreatment and the imposition of forced labour inside the camps was in part the result of the contradictory aims of the entire system. These contradictions are probably intrinsic to all major labour camp systems, and we find them unsurprisingly also in the Soviet GULag system, where 600,000 people died during WWII.
The Nazis continued to distinguish strongly between labouring and non-labouring prisoners, but the types of work demanded from KZ inmates changed. Working on construction sites digging tunnels for underground factories, as at Dora-Mittelbau, was going to be a
mankiller pretty much come what may.
Women prisoners assigned to sit down work in factories are going to have a higher survival rate just by the nature of the work.
In 1944-45, the greatly expanded camp system designated a number of sub-camps, and eventually even an entire camp, as essentially a dumping ground for worn out, exhausted inmates. Some of the worn out inmates were murdered in gas chambers at Ravensbrueck and other camps, others simply sent to the dumping ground camps.
The biggest such camp was Belsen, but Belsen also served as a holding camp for exchange prisoners, and was subdivided into various different camps. That's why some prisoners could be liberated from Belsen in decent shape whereas the majority were not; they were the lucky survivors of multiple decisions to transfer worn out prisoners and evacuation transports to a single site, which rapidly became overcrowded and thus an ideal incubator for a typhus epidemic. The same thing had happened
on the same site in 1941 when the Nazis mishandled the transfer of Soviet POWs to Germany.
(the last paragraph will surely sail over Saggy's head, and I predict a pointless repetition of his usual blether, but it needs saying nonetheless for the benefit of sane people.)
It's pretty important to understand that the Nazis used a wide variety of systems to incarcerate different people for different purposes, and that there were substantial transfers between the systems. Prisons still functioned in the war, and held German as well as non-German inmates. The death rate rose considerably during the war, and reached fairly substantial levels in e.g. the Emsland camps on the North German moors. Germans and non-Germans were sentenced to prison for punitive reasons, as is hardly unknown in human history. The same prisons also held inmates awaiting execution, and the rate of executions also rose during the war. Obviously, decisions were made to kill some people when a strictly rational choice would have been to keep them alive to work. But the same decisions were made in other contexts - eg in Stalinist Russia, that place you hate to compare this stuff to.
In the occupied territories, there were even more prisons, and because rations were generally lower in the occupied territories, especially in Eastern Europe, the death rates were very high there, too. Plus those prisons and prison camps were also frequently sites of large scale serial executions. But then in the eyes of the Nazis, Poles and Russians needed killin' in larger numbers to whup their asses and make the Untermenschen into obedient little slaves.
Eventually, in early 1943, Himmler decided to allow prisoners to be transferred from occupied Soviet Union to concentration camps in Poland and Germany. This was a 'concession' to the labour shortage, or rather a way for Himmler to build up 'his' workforce in the KZs. At the same time, Himmler also ordered an increased rate of arrest for foreign workers in Germany, for entirely selfish reasons. By 1944 Speer complained about this, since 10s of 1000s of foreign workers were being arrested in Germany every month and sent to the concentration camps, where quite a few died. From a strictly rational perspective this was dysfunctional, but other than imbeciles, nobody ever thought that governments, much less the Nazi regime, are entirely rational.