During World War II, Irena Szydłowska was a courier for the Polish Home Army, an underground force that fiercely resisted Nazi occupiers. On 14 January 1945, records show, she was arrested by the Gestapo. Days later, with defeat looming for Germany and Soviet forces on the horizon, she and hundreds of other Home Army fighters were taken from prison and marched into the forests of northern Poland. Szydłowska, 26, left behind a 4-year-old son.
Witness reports collected after the war suggest what happened next: Szydłowska and her fellow prisoners were gunned down by German soldiers who stacked their bodies, doused them in gasoline, and burned them on massive pyres that lit up the forest for 3 days and 3 nights. The ashes were pushed into shallow pits and covered. Then, for 75 years, the site of the mass grave was lost.
Now, archaeological excavations near the Polish village of Chojnice have uncovered physical evidence of that massacre and a previous one, recovering victims’ jewelry, bullet casings, burnt human bones, and more. “We knew the victims were buried somewhere, but until our research no one knew where,” says archaeologist Dawid Kobiałka of the Polish Academy of Sciences’s Institute of Archaeology and Ethnology, whose team used everything from archival documents and interviews with survivors to laser scans and excavations.
Colleagues say the research, reported this week in the journal Antiquity, is the first to systematically apply archaeological techniques to a World War II–era mass grave outside of concentration camps, where research on human remains is often prohibited by Jewish religious belief. Although there were many similar massacres, “There hasn’t been research so far on a World War II site like this,” says University of Vienna archaeologist Claudia Theune. “It adds another category of crime scene.” Legal inquiries trigger most war crime investigations, adds archaeologist Alfredo González-Ruibal of the Institute of Heritage Studies of the Spanish National Research Council. This one was initiated by researchers and is one of the few to be published in a scientific journal, he says.
Kobiałka grew up Chojnice, where he heard locals refer to the swampy forest just a few hundred meters from his childhood home as “Death Valley.” The area was a palimpsest of horror: In 1939, advancing German forces rounded up and executed Polish priests and intellectuals, Jewish families, and disabled people, then buried them there in a long line of trenches the retreating Polish army had dug for defense. More than 100 victims of those killings were found after the war and reburied. But hundreds more remained unaccounted for, along with about 500 people killed in January 1945. Kobiałka thought the methods of archaeology might help reveal what happened and where. “I was fully convinced mass killings like that must leave behind a lot of material culture.”
His team first dove into archives to find reports of the forced march. They interviewed survivors, including several whose parents were killed in 1939. They also matched aerial photos taken by the Allies in the closing days of the war with laser scans of the modern forest floor taken from an airplane, and spotted a trench line beneath thick vegetation. Then they used ground-penetrating radar and other noninvasive techniques to pinpoint soil disturbances that might indicate burial pits along the trench. All this led them to focus on a wooded area on the edge of town.
There, in July 2020, they used metal detectors to uncover a dense collection of bullet shells, buttons, cuff links, a wristwatch stopped a few minutes after 5 o’clock—and Szydłowska’s wedding ring, which a historian identified based on the wedding date and initials engraved inside. The topsoil held pieces of burned human bone. “We used every possible archaeological method,” Kobiałka says. The evidence convinced him they had found the site of the 1945 massacre.
Yet the valley’s overlapping atrocities, and the lengths the Nazis went to conceal them, made it hard to be sure. The site is “very complex,” González-Ruibal says. “It was used at different times and evidence was destroyed, but they’ve still been able to retrieve a lot of information and even identify people.”
With additional funding from the Ministry of Culture, National Heritage and Sport, Kobiałka’s team returned to Chojnice this summer. Over the past few months, the researchers excavated three burial pits filled with ash, bone, and more than 4000 artifacts, including hundreds of shells, all presumably from the 1945 massacre. They found valuables including medallions, cigarette lighters, and another engraved gold wedding ring, suggesting Nazi soldiers were more interested in covering up their crime quickly than in looting bodies.
Researchers also recovered more than 1 ton of human bone. “That amount seems to confirm the historical records that 400 or 500 people were killed and burned” in the 1945 massacre, Kobiałka says. “I’m an experienced archaeologist, but I’ve never experienced anything like this. It was really a horror.”
The team plans to analyze the bones before reburying them in Chojnice, hoping DNA might help identify victims and surviving relatives. But exhuming victims can be fraught, cautions Susan Pollock, an archaeologist at the Free University of Berlin who has excavated World War II–era sites in Germany. “The authors imply that recovery and analysis of all remains will serve the interests of families as well as of justice,” she wrote in an email. “I would still ask who sees it this way, and if some of the potential victims and their families do not.” Kobiałka notes the excavations were carried out with the permission of Poland’s Institute of National Remembrance and the support of the local community. He adds that few if any victims of the 1945 massacre were likely to be Jewish, and that local Jewish victims killed in 1939 were exhumed and accounted for after the war.
Mixed in with the bone in the woods, the team recovered more than 500 pieces of charcoal and partially burned wood. Analysis showed the fragments were common pine, a species that didn’t grow in the swampy soil of Death Valley during World War II and must have been brought in to make the pyres, Kobiałka says. The team hopes to analyze chemicals preserved in the wood to confirm the use of gasoline or another accelerant to stoke the pyres.
A final piece of the puzzle came from analysis of more than 400 recovered bullets and shell casings, which a ballistics expert identified as rounds from pistols commonly used by the Gestapo and German police units; the use of pistols suggests the victims were shot one by one at close range. “It’s important that they found evidence about the people who were killed and the perpetrators,” Theune says. “They found evidence it was a Nazi crime.”
The research offers a possible model for other excavations, suggesting the crimes of the past are part of archaeology’s future. “Investigating … crimes against humanity is a huge challenge for excavators,” González-Ruibal says. But, “It’s more important than ever to learn what happened.”
Szydłowska’s son survived the war but died in 2004, never knowing his mother’s fate. But prosecutors have now located his daughter, hoping to close a painful chapter in the family’s history.