The following is an excerpt from the article linked below it :

‘The Dachau concentration camp was used by the Nazis for many of its most hated enemies. Among them were Catholic priests. Indeed, of the 2,720 clergy sent to Dachau, 2,579 were Catholic priests, along with uncertain numbers of seminarians and lay brothers. Most were Polish priests, 1,748 in all; there were also 411 German priests. Of the 1,034 priests who died in the camp, 868 were Polish. The priests were housed in a special “priest block” and were targeted for especially brutal treatment by the SS guards.

It is estimated that at least 3,000 other Polish priests were sent to other concentration camps, including Auschwitz, while priests from across Europe were condemned to death and labor camps: 300 priests died at Sachsenhausen, 780 at Mauthausen, and 5,000 at Buchenwald. These numbers do not include the priests who were murdered en route to the camps or who died from diseases and exhaustion in the inhuman cattle cars used to transport victims. Several thousand nuns were also sent to camps or killed on the way.

The list of victims is a very long one, and the suffering on a daily basis by the priests is unimaginable. For many, the ordeal lasted for years. Adam Kozlowiecki, a Polish priest, was arrested by the Gestapo in November 1939 and was sent to Auschwitz in 1940; transferred to Dachau in December 1940, he spent the next five years there until he was freed by the U.S. army on April 29, 1945. Kozlowiecki was made a cardinal in 1998. A few of the other notable priests at Dachau were Bl. Michal Kozal, Bl. Stefan Grelewski, Bl. Stefan Frelichowski, Bl. Karl Leisner, and Bl. Titus Brandsma.’

https://www.catholic.com/magazine/print-edition/catholic-martyrs-of-the-holocaust