A letter that spent decades buried underground recounts the horror of a Jewish man forced to move the bodies of his fellow prisoners at Auschwitz.

Marcel Nadjari, a Jewish merchant from Greece deported by the Nazis to the death camp in Poland, buried his account in a thermos, hoping that one day it might tell his family and the world about the brutality there.

The letters were near completely illegible when the thermos was uncovered in 1980, though historians using a new imaging technique have now been able to reconstruct what Nadjari said about working at the camp’s gas chambers.

After deciphering the letter, Russian-born historian Pavel Polian is set to publish his findings in the Munich-based Institute of Contemporary History’s magazine this month, German and Swiss media reported.

Nadjari, who ended up surviving the Holocaust, moving to the United States and dying in New York in 1971, was assigned to the “Sonderkommando” unit of prisoners that took bodies from the gas chambers and burned them in a crematorium.

Participants of the yearly March of the Living place memory plaques on the rails in the former German Nazi death camp Auschwitz-Birkenau. (ALIK KEPLICZ/AP)

“If you read about the things we did, you’ll say, how could anyone do that, burn their fellow Jews?” he wrote, according to Deutsche Welle, adding “That’s what I said at first, too, and thought many times.”

Nadjari said that several times he thought about going into the gas chamber himself to end his life, but that he was motivated to live by the desire for revenge.

Polian told DW that documents buried by Nadjari and a handful of other “Sonderkommando” prisoners are “the most central documents” for learning what occurred during the Holocaust.

The historian was assisted by Russian technology expert Aleksandr Nikitjaev, who used different wavelengths of light corresponding to red, green and blue to create greater contrast in the illegible letters and read them. NYDN