On June 22, 1941, the German armed forces launched the biggest invasion operation in history, crossing the border into the Eastern European countries occupied by the Soviet Union under Stalin, and penetrating within a few months to the gates of Moscow and St. Petersburg. Millions of civilians were killed, their villages and towns burned to the ground, their food supplies sequestered, the basic infrastructure of their daily lives shattered. Three and a half million soldiers taken prisoner by the German forces were left to die of starvation and disease. But a special fate was reserved for the two and three-quarter million Jews who lived in the area conquered by the Germans.

Within a few weeks of the invasion, killing squads of the black-shirted SS were roaming the countryside shooting Jews by the thousand. Within a few months, the SS was complaining of the nervous strain this was causing on the killers, and the slowness with which they were carrying out their murderous task, so mass gassing facilities were constructed to speed the process up and render it more impersonal. Eventually, more than two and a half million of the Jews in German-occupied Eastern Europe were killed.

For decades, relatively little was known about this killing operation, vast in scale and scope though it was. For the Soviet Union, the victims were Soviet citizens first and last, and the latent — and sometimes, as in the early 1950s, open — anti-Semitism of the Russian leaders prevented any recognition of the fact that they had been killed not because they were Russians or Ukrainians but because they were Jews.

At the end of the war, however, two Soviet journalists of Jewish origin, Ilya Ehrenburg and Vassily Grossman, determined to collect as much testimony as they could about these murders, to use it in anti-German propaganda and to preserve it for posterity. Grossman won worldwide fame posthumously as the author of “Life and Fate,” one of the greatest war novels of all time, suppressed for many years by the Soviet regime. Ehrenburg became famous in his own lifetime, a reporter and propagandist of genius whose newspaper articles made him a national hero and did an enormous amount to boost morale among Soviet soldiers and civilians alike. Together with Grossman, he organized reporters to visit the sites of massacres and collect testimony from survivors. Many Jews also wrote to him about their sufferings. The result was a massive collection of eyewitness reports, documenting with raw immediacy the genocidal campaigns of the Germans in Eastern Europe just a few months after they had come to an end with the defeat of the German forces by the Soviet armies.

Ehrenburg and Grossman put much of this material together in a volume they called “The Black Book,” but the Soviet authorities considered that many of the testimonies contained too much detail on the participation of Ukrainians, Romanians, and others in the killings, and so distracted attention from the Germans, and thus undermined the collection’s power as propaganda. These testimonies were removed from “The Black Book,” which was nevertheless suppressed because of “grave political errors,” and which remained unpublished until the late 1970s. It was not until the fall of communism in 1990 that the missing testimonies could finally appear in what Ilya Altman, their editor, called “The Unknown Black Book” (Indiana University Press, 446 pages, $34.95), now made available here in an English translation by Christopher Morris and Joshua Rubenstein.

The material ranges from brief interviews to lengthy diary extracts, from rambling and confused letters by simple folk to elegant literary narratives typewritten by schoolteachers and highly educated professionals. The world they conjure up is one of almost unimaginable suffering and continual violence and atrocity. What strikes one again and again when reading them is the special hatred and venom reserved for the Jews by the anti-Semites of all the nations involved: This was not just mechanical killing, but killing accompanied by brutal violence, visceral hatred, and deliberate, often sadistic acts of humiliation. The Romanians, for instance, deliberately shut up thousands of Jews in a huge state pig farm, and committed atrocities so vile that even the SS complained about them. Much of the testimony collected in “The Unknown Black Book,” indeed, is almost unbearable to read.

Despite the extensive documentation here of the heavy participation of Romanian, Ukrainian, Latvian, and other anti-Semites in the genocide, it would be misleading for the book to suggest that all the inhabitants of these countries were consumed by murderous hatred of the Jews in their midst. In fact, except in Romania, those who took part were only a tiny minority. SS officers charged with carrying out the brutal operation were soon complaining that it was very difficult to find local anti-Semites who would act as surrogates and do the work of killing for them.

This point is clearly made in Joshua Rubenstein’s helpful introduction, which sets the testimonies to follow in their context and provides essential background material. As Mr. Rubenstein notes, the people who told their stories to Ehrenburg and his team had cheated death by a variety of means, running from the killing fields, hiding under heaps of dead bodies, concealing themselves in attics or cellars, disguising themselves as non-Jews, taking refuge among friendly and sympathetic villagers; the stories of survival they tell here provide some of the most dramatic and astonishing episodes in this book. But these are not triumphant narratives with happy endings. All of the people whose testimony is reproduced here lost loved ones, friends, and families, and went through almost unendurable suffering. “Every human being was broken,” as one of them wrote, “shattered, and envious of the dead.”

Mr. Evans is a professor of modern history at the University of Cambridge and the author of “The Third Reich in Power.” His book “The Third Reich at War” is forthcoming from Penguin Press.