By Vivienne Walt ~ LVOV and REVA-RUSKA 

Treading across a snowy field in the middle of the Ukrainian town of Rava-Ruska, Olga Kushta says quietly: “This is where they were shot. I watched all the killings.”

Sixty-four years have passed since Kushta stood by the roadside with her teenage friends, watching Nazi soldiers day after day as they led some 5,000 Jews from the town to the rim of a giant pit, and shot them in the back at point-blank range. Kushta, now 78, says she still replays in her mind the moment when a close friend of her mother’s passed by and pleaded with her for help. Drawing her woollen scarf around her head in the frigid December morning, Kushta asks: “How could I save her? I was only a child.” That night she told her parents what she had witnessed. And then, for more than six decades, she never spoke about the killings again.

But the long silence — from Kushta and hundreds of other witnesses — has finally ended, thanks almost entirely to one man. His extraordinary four-year quest to document the country’s mass executions has shattered decades of secrecy and denial about the slaughter of Jews that occurred after Nazi Germany invaded Ukraine in 1941. In 2002 Patrick Desbois, a Catholic priest from Paris, visited Rava-Ruska for the first time, intrigued by tales he had heard from his grandfather as a boy. The older man had been a prisoner of war in the town in the early 1940s, and had told young Patrick that horrors had occurred there. When Desbois arrived in Rava-Ruska — a town of about 8,000 a few miles from the border with Poland — to learn what had happened, “it was like a black hole,” he says. “There was nothing in the books.”

Desbois says the then mayor declined to divulge details. But when the priest returned a year later, the deputy mayor, Yaroslav Nadiak, led him to the forest of Borowe outside the town and revealed what Rava-Ruska’s townsfolk had long known: that

some 1,500 Jews had been shot and hastily buried in a mass grave there in November 1943. “He told me: ‘Patrick, I could take you to a hundred villages like this,'” says Desbois. “And I said: ‘OK. Let’s go.'”

In fact, the number was far higher than that, and Desbois admits he had little idea of the huge task he had set himself when he began his full-time research in 2004. In 15 trips to Ukraine, the 52-year-old priest has since located more than 750 killing sites, some of which contain several mass graves, and he now suspects there may be another 1,800 graves scattered across the country. Ukraine’s graves — many of them just depressions in the ground, suggesting the weight of hundreds of bodies — were neglected through decades of Soviet rule. Now, with many of the Holocaust’s witnesses in their 70s and 80s, Desbois feels he is running out of time. “In five years,” he says, “there will be no more witnesses.”

A short, dark-haired man with a fiery intensity and stubborn tenacity, Desbois heads a nonprofit organization in Paris called Yahad-In Unum, which promotes Catholic-Jewish relations. With his mission approved by France’s Catholic bishops, he has traveled thousands of miles through remote Ukrainian villages, his priest’s collar helping to put locals at ease in places where foreigners are rarely seen. Desbois taught mathematics in West Africa before becoming a priest, and later worked in Algeria; he also studied Hebrew in Jerusalem, and he serves as an advisor to the Vatican on Jewish affairs. But none of that prepared him for his charged work in Ukraine’s villages, where the bottled-up emotions of aging Ukrainians pour out as they describe the executions they saw, and share details that some of them have kept even from their spouses. “It’s like they have been waiting for years to talk,” says Desbois. “They always ask: ‘Why have you come so late?'”

Historians have long known that the Holocaust involved mass executions, as well as concentration camps. Yet despite the mountain of literature, films and photographs documenting the Holocaust, Desbois has filled in a crucial missing piece of history by interviewing hundreds of people who witnessed the Ukrainian killings firsthand. “The testimony is just unbelievable,” says Paul Shapiro, director of research for the U.S. Holocaust Memorial Museum in Washington, which is honoring Desbois at a dinner in the capital in April.

The Simon Wiesenthal Center, a Jewish-rights organization in Los Angeles, is awarding Desbois a Medal of Valor in May. The center’s international director, Shimon Samuels, says Desbois’ findings might even cast doubt on the long-accepted estimate that 6 million Jews died in the Holocaust, since “he’s found killing sites we never knew existed.”

For years, Holocaust researchers have relied heavily on accounts from Jewish survivors, and on official German and Soviet archives; about 16 million pages of Soviet reports are now housed in the Holocaust Memorial Museum. But Desbois has taken Holocaust research in a new direction. As he sees it, his work is more like “a police investigation,” in which he tracks down eye witnesses, cross-checks their stories, and hunts for graves and bullet shells. The resulting voices of hundreds of witnesses provide a window into how a well-organized genocide could occur in these Ukrainian communities with no one choosing, or able, to stop it. That provokes profound questions about culpability and powerlessness, and the possibility of future genocides, which resonate far beyond 1940s Europe, say researchers like Shapiro. Explaining why it has taken so long to uncover such testimony, Shapiro says: “Frankly, no one ever went there before.”


Unearthing the Truth

Unlike the industrial-scale, anonymous genocide in death camps such as Auschwitz — the world’s iconic images of the Holocaust — Ukraine’s killings were often terrifyingly intimate. While 400,000 Ukrainian Jews were murdered in concentration camps, about 1.1 million were shot dead at close range. The murders were often in full view of neighbors and acquaintances, many of whom the Nazis deployed to dig and cover the graves, then to distribute the belongings of the dead. The fact that locals sometimes received these possessions, or were ordered to help in the executions, may partly explain their long silence, says Desbois. Tapping into the country’s nationalistic animosity toward its Soviet rulers, the Nazis found plenty of helpers among Ukrainians. According to the 1996 book Hitler’s Willing Executioners by Daniel Jonah Goldhagen, many Ukrainians participated in the Nazi killings of Jews during pogroms in Ukraine’s villages. Some Ukrainians also helped to run Nazi concentration camps. This persecution by their own countrymen left deep bitterness among Ukrainian-Jewish Holocaust survivors, says Lee Schein, 77, who fled Rava-Ruska during the war as a 12-year-old girl, and now lives in Glen Ellen, California. “The Nazis offered the Ukrainians their own state if they worked with them, so they worked with them,” she says. “It is a pure miracle that I got away.” But Desbois insists he is not looking to assign blame. “I do not ask who is guilty and who is not guilty,” he says. “I deal just with victims.”

The stories from Desbois’ witnesses have beeneye-opening for younger Ukrainians too. Under the Soviet Union, the official line was that World War II was a battle between communists and fascists. The Nazis’ “Final Solution” program to exterminate Jews was rarely mentioned. And although Holocaust teaching is now officially on the syllabus of Ukrainian schools, many of the nation’s youth remain ignorant of what their grandparents lived through.

In the Lisinichi Forest outside the city of Lviv one day in late December, Adolf Wislowski, 77, leaned on his heavy walking stick and described for Desbois how as a child he would climb a tree and watch Nazi soldiers shoot thousands of Jews; the killings lasted for about six months. Since Wislowski’s school was close to the forests, he and his classmates kept careful track of the executions, observing closely how the Nazis led the Jews to the edge of the trees, then shot them in small groups. Near the end of the war, the Nazis ordered Jewish prisoners to burn the corpses in the forests in a hurried attempt to erase the evidence before Germany’s retreat from Ukraine in 1944. “Columns of smoke rose until we could barely breathe,” said Wislowski, describing the massive burning program. Historians believe about 90,000 people lie in more than 40 mass graves tucked among the trees of the Lisinichi Forest, including hundreds of Italian soldiers killed by the Nazis after Italy surrendered to the Allied forces in 1943.

These days, local children play in the forests, unaware of the grim history beneath their feet. As Wislowski spoke to Desbois, two boys squatted on the ground nearby, listening intently, and afterward told TIME that they had known nothing of the killings until then. Although Jews were overwhelmingly the largest group of victims, the Nazis also shot tens of thousands of Gypsies, as well as Polish and Soviet citizens and Italian soldiers. A 26-year-old Ukrainian translator for Desbois said she knew of those deaths, but was astonished to learn about the mass killing of Jews when she met the priest last year.

Many of the stories that Desbois has uncovered took place in remote, desolate country villages that today seem frozen in a bygone age; they still have little electricity and no indoor plumbing. On New Year’s Day, TIME traveled with Desbois to the tiny village of Vysotsk in northern Ukraine, a few miles from the Belarus border. We drove for nearly eight hours from Rava-Ruska through the countryside in temperatures approaching -4 degrees F (-20 degrees C). In the back of his rented van, Desbois pored over translations of documents from 1944 when Soviet officials went to Vysotsk to question villagers. Their report, now housed in the U.S. Holocaust Memorial Museum, makes grim reading: in 1942, the Nazis gathered all of Vysotsk’s 2,000 Jews and marched them to a giant pit, where they shot them in groups of five. The report estimated that 1,864 people died on a single day, with children buried alive in order to save bullets.

In Vysotsk — today a cluster of wooden houses with horse-drawn carts and creaking outdoor wells — a woman directed us to a memorial on the edge of the village. There, a large grave site was fenced off, and a Russian plaque announced that 1,864 Soviets — not Jews — were killed in 1942. So Desbois began knocking on doors along the one narrow road running through the village, in search of any witnesses to that day in 1942. “Were you living here during the war?” he asked as residents emerged from their homes, startled at the sight of an outsider. As darkness fell, Hanna Dvurinska, 79, invited us into her tiny wooden house. There she told Desbois how she had watched — as a 14-year-old girl — from her parents’ living room window, as Vysotsk’s Jews were led down the road to a freshly dug grave; hours of gunshots followed. “Some of them were carrying their possessions,” she said through a translator. “They knew they were going to be shot.” A few doors down, Iarino Hanitko told Desbois that she remembered that day clearly, especially as her parents had hidden a Jewish boy in the house; the boy escaped the Holocaust and emigrated to the West. As Hanitko watched the columns of Jews on their way to the grave, she saw some of them being shot while trying to escape.

In this remote village, few people are still alive who can bear witness to these horrors, and it may be too late to correct the misinformation carved into the Soviet plaque beside the mass grave. But elsewhere, Desbois has used his dogged persistence to commemorate the execution of Jews before all recollection of them is lost forever. In late December, Yaroslav Nadiak, Rava-Ruska’s former deputy mayor, hired workers to lay a cement gravestone with a Jewish star in Borowe, a village on the edge of town, atop the mass grave containing about 1,500 Jews — the one Nadiak had first revealed to Desbois in 2003, setting the priest on his long quest for the truth. On the last Sunday in December, a group of Ukrainian Jews drove to Rava-Ruska from Lviv, an hour away, and gathered in the snow around the grave, where they recited Kaddish, the Jewish prayer for the dead. For Desbois, this quiet ceremony in the woods was a high point after his years of wrenching work. “I want to see these people properly buried,” he says. And to know that the truth about how they died will not be buried with them.

Read this story on TIME Magazine.