The researchers have cataloged some 42,500 Nazi ghettos and camps throughout Europe, spanning German-controlled areas from France to Russia and Germany itself, during Hitler’s reign of brutality from 1933 to 1945. The figure is so staggering that even fellow Holocaust scholars had to make sure they had heard it correctly when the lead researchers previewed their findings at an academic forum in late January at the German Historical Institute in Washington.
“The numbers are so much higher than what we originally thought,” Hartmut Berghoff, director of the institute, said in an interview after learning of the new data.  “We knew before how horrible life in the camps and ghettos was,” he said, “but the numbers are unbelievable.”
The documented camps include not only “killing centers” but also thousands of forced labor camps, where prisoners manufactured war supplies; prisoner-of-war camps; sites euphemistically named “care” centers, where pregnant women were forced to have abortions or their babies were killed after birth; and brothels, where women were coerced into having sex with German military personnel. 

Auschwitz and a handful of other concentration camps have come to symbolize the Nazi killing machine in the public consciousness. Likewise, the Nazi system for imprisoning Jewish families in hometown ghettos has become associated with a single site — the Warsaw Ghetto, famous for the 1943 uprising. But these sites, infamous though they are, represent only a minuscule fraction of the entire German network, the new research makes painfully clear.
The maps the researchers have created to identify the camps and ghettos turn wide sections of wartime Europe into black clusters of death, torture and slavery — centered in Germany and Poland, but reaching in all directions.
The lead editors on the project, Geoffrey Megargee and Martin Dean, estimate that 15 million to 20 million people died or were imprisoned in the sites that they have identified as part of a multivolume encyclopedia. (The Holocaust museum has published the first two, with five more planned by 2025.) [...]