I have written about this subject before here and the gist of it is that Black PoWs were often transferred to Concentration Camps and experimented upon but not shot on the spot like Jewish Soviet soldiers or – for some time – soldiers from the Central Asian Repoublics of the USSR.
The lives and experiences of Black people in Nazi Germany
As one probably can imagine, life in Nazi Germany was not very good for the about 20.-25.000 Afro-Germans, African or African Diaspora living in the Third Reich by 1933.
Information and numbers on who these people were differ apparently, however a considerable percentage of the Black individuals living in Germany were from Namibia or other former German colonies while another part were the children of German women and French-African soldiers who were stationed in Germany during the occupation of the Rhineland. These "Rhineland Bastards" were probably the group the German racial discourse concerning Black Germans revolved around. Seen as a product of a loathed occupation and additionally as an example of the "pollution" of the German "race", these individuals were probably the most discriminated against of all the Black people living in Germany.
Hitler wrote about them in Mein Kampf: “Jews were responsible for bringing Negroes into the Rhineland, with the ultimate idea of bastardizing the white race which they hate and thus lowering its cultural and political level so that the Jew might dominate.” Together with all other Black people, the "Rhineland Bastards" were deemed non-Aryan under the Nuremberg laws and therefore forbidden from marrying "Aryans".
Additionally, they were forced to undergo sterilization from 1937 on. Organized by the two most prominent German eugenicists, Eugen Fischer and Fritz Lenz, about 400 children deemed as "Rhineland Bastards" were forcibly sterilized from 1937 on.
Beyond that there was no coherent policy of Nazi Germany towards Black people except a campaign for social isolation, which given the racially charged climate of the time and the use of Black people (espeically in the context of Jazz) as a signifier for the degeneracy of the USA, hardly needed help. Black people were forbidden from entering University, lost their jobs and were ostracized. Beyond that no coherent policy was ever formed. Robert Kestings describes a case in which a local labor agency petitioned the Reich Security Main Office on how to deal with an Afro-German who was unable to find employment due to his criminal record and got the response that the population was too small to warrant the formulation of an overarching policy and therefore they could deal with it as they saw fit.
Beyond that, experiences differed to some extent, especially in the context of the war. There was a small number of Black soldiers serving in the Wehrmacht through recruitment during the African campaigns but as a general rule, Black POWs of various Allied Armies were treated worse than their non-Black counterparts. Black POWs were often transferred to Concentration Camps and various survivors report that they were subjected to cruel medical experiments because they were Black.
As a last group that often gets ignored, there were Black Jews suffering from Nazi German policies. Especially in North Africa, Black Jews were used for forced labor and often send to Concentration Camps. All in all they probably numbered around 5.-6.000 and we hardly have any testimonies from this particular group.
As for a more direct response to your question: It is very difficult to gauge the numbers of how many Black people were imprisoned in Concentration Camps. A preliminary research of the German Bundeszentrale for political education has found 34 civilian Black prisoners in Concentration Camps. Three of them, Johnny Nicholas, Josef Nassy and Mohammed Husen, have had literature published about them that I don't have at hand atm.
Paulette Anderson in her book * Eine Geschichte von mehr als 100 Jahren: Die Anfänge der afrikanischen Diaspora in Berlin. Berlin 1995* has estimated that there might have been up to 2000 Black people in concentration camps but nobody can be certain of definitive number not only because records are missing but also because it can be assumed that very very few survived the camp.
Treatment can be assumed to have been worse than that of many of the White Prisoners. Lusane mentions a Black female prisoner of Ravensbrück who was subjected to medical experiments that in essence amounted to frequent rape in order to see if Blacks were "more fertile". Also if treatment of Black POWs is any indication, we can also assume that the treatment was much worse. Lusane lists a sample number of deadly violence against Black POWs:
February 20, 1944: In Salzburg, Austria, a Dr. Prima, who may have been in the SS, was accused of coming upon wounded African American airmen and summarily executing them.
May 5, 1944: In Budapest, Hungary, near a local prison, the Gestapo hanged three African American pilots to death. Hitler’s black victims
(On or about) September 1, 1944: Near Merzig, Germany, black American soldiers were ordered to dig their own graves and th en shot. It is also alleged that perhaps another 20 black American soldiers were take n to a nearby forest and executed there.
December 17, 1944: Near Wereth, Belgium, 11 African American solders of the 33rd Field Artillery Battalion were murdered, alle gedly by members of the 1st and/or 2nd Panzer Division. Among the killed were Curtise Adams, Mager Bradley, George Davis, Thomas Forte, Rob Green, Jim Leatherwood, Nathaniel Moss, George Motten, and William Pritchett.
December 18, 1944: In Sopron, Hungary, at a local jail, a black American pilot was executed without cause or explanation. • (On or about) December 18, 1944: Near Muehlberg, Germany, while being marched to Stalag IV-B, a black American soldier was singled out and killed by the SS.
April 1, 1945: In Moosburg, Germany, at Stalag VII-A, a SS guard was alleged to have executed a black American, with no excuse being given.
In general, I would recommend Clarence Lusane's book since he also has more on the known Black survivors of the Concentration Camp system and goes further into what they recall about their treatment.
A last topic I want to mention is the fate of the Black children of American GIs after World War II: These kids often experienced a terrible fate. The German and Austrian authorities took the stand point that their mothers were unfit to raise them and the vast majority was taken away from their mothers and either send to family members in the US or given to other families. A lot of research into this topic is done right now but from what we can tell a lot of their experience includes social isolation, not knowing who one's family is and being othered in a very racially homogeneous society.
Sources:
Campt, Tina. Other Germans: Black Germans and the Politics of Race, Gender, and Memory in the Third Reich. Ann Arbor: University of Michigan, 2004.
Friedman, Ina R. “No Blacks Allowed.” In The Other Victims: First-Person Stories of Non-Jews Persecuted by the Nazis, 91-93. Boston: Houghton Mifflin, 1990.
Kesting, Robert (2002). "The Black Experience During the Holocaust". In Peck, Abraham J.; Berenbaum, Michael. The Holocaust and History: the Known, the Unknown, the Disputed, and the Reexamined. Indiana University Press.
Robert W. Kestling: Blacks Under the Swastika: A Research Note , The Journal of Negro History, Vol. 83, No. 1 (Winter, 1998), pp. 84-99
Lusane, Clarence. Hitler’s Black Victims: The Historical Experiences of Afro-Germans, European Blacks, Africans, and African Americans in the Nazi Era. New York: Routledge, 2002.
Maria Höhn: GIs and Fräuleins. The German-American Encounter in 1950s West Germany. University of North Carolina Press, Chapel Hill NC u. a. 2002.
Further information can be found at the USHMM's Online Exhibition about Black experiences in Nazi Germany