Marianne Szegedy-Maszak is the editorial operations director in the Washington bureau of Mother Jones and the author of “I Kiss Your Hands Many Times: Hearts, Souls, and Wars in Hungary.”

Seventy years from now, how will the migrant children detained at our southern border describe what happened to them? What will the 3-year-old girl who was separated from her parents recall of her panic at that moment? Will images of her mother and father be eclipsed by the scent and uniform of an immigration agent? Will the little boy who was 9 remember the day that toothbrushes and toothpaste finally arrived as being notable? As an old man, will he look at a baloney sandwich and feel a bit sick, for reasons he can’t quite understand? Did he make a friend? Were adults kind or cruel or both?

Our memories of childhood are generally impressionistic, mostly consisting of vast blank periods of time marked by inexplicably vivid moments, as if the instant were suspended in formaldehyde and preserved far away from its chaotic natural habitat. But when those memories are forged in times of trauma, the fact that they are impressionistic infuses the details with even greater significance. In the midst of all that was obliterated, their endurance in the face of unimaginable odds is a kind of victory. There is a vast literature by adults transforming their traumatic childhoods into art. Frank McCourt’s miserable childhood in Ireland depicted in “Angela’s Ashes,” or Eli Wiesel’s adolescence in Auschwitz chronicled in “Night,” or Ishmael Beah’s experience as a child soldier in Sierra Leone portrayed in “A Long Way Gone” are transcendent works by gifted writers. But what about the experiences of the others? The millions who became laborers, doctors, locksmiths, seamstresses, teachers. What do they remember of catastrophic times? What is unlocked when someone bothers to ask?

From 1978 to 2004, Nobel Prize-winning Belarusian author Svetlana Alexievich bothered to ask scores of adults who were children during the 1,418 days when the Soviet Union was decimated by, and ultimately victorious in, World War II. What she learned appears in her new book, “Last Witnesses: An Oral History of the Children of World War II.” An estimated 26 million to 27 million others, mostly civilians, many of them children, perished in the Soviet Union. Alexievich has collected 101 stories of those who, through the ineffable and arbitrary winnowing of the doomed and the saved, survived. Their stories appear in fragments of only a few ellipses-filled pages, each beginning with a quotation from the narrative, the person’s name, profession and age in June 1941 — when Operation Barbarossa, the German campaign to defeat the Soviet Union, began. Those quotations appear in the table of contents, and even a random series strung together reads like an elegiac tone poem: “A handful of salt … all that was left of our house” / “And I kissed all the portraits in my schoolbook”/ “I gathered them with my hands … they were very white” / “I want to live! I want to live!”

This is familiar territory for Alexievich and another example of her often-controversial approach to storytelling, which she deployed when writing about the horrors of the Afghan war, Chernobyl, women in World War II and the last days of the Soviet empire. There is not much contextual narrative; no clear authorial voice intervening to explain what her subject is describing; no nod to how she found these people, how many days she spoke to them or her methodology. Instead, she is at once interviewer, reporter, oral historian, stenographer, interlocutor and ghostwriter, rendering with painful immediacy the memories of those with whom she spoke. She calls her books “novels in voices,” and on the author’s page of this book, she is described as having “developed her own nonfiction genre, which brings together a chorus of voices to describe a specific historical moment.” Though she began her career as a journalist in Minsk, she no longer considers herself one and rejects the categories of historian, novelist, reporter, while touching on all of them.

When she won the Nobel Prize for literature in 2015, her citation noted “her polyphonic writings, a monument to suffering and courage in our time.” But critics have stressed that there is no fact-checking, nor methodology, and the interviews have all been massively, unapologetically edited, with the result that, as Sophie Pinkham pointed out in the New Republic in 2016, “by seeking to straddle both literature and history, Alexievich ultimately succeeds at neither.”

Strictly speaking, that’s true. But questions regarding professional disciplines do nothing to diminish the power of what she has created in “Last Witnesses,” as she excavates and briefly gives prominence to demolished lives and eradicated communities. Her subjects lived in the blood-soaked villages of Belarus and Ukraine, where the victims of combat between Germans and Russians included Poles, Jews, Russians and a complex stew of ethnicities. The parents of a number of these children were Soviet partisans — members of a guerrilla resistance movement that was especially fierce in occupied Poland. In the midst of it were places unfamiliar to most Westerners — Belynichi, Smolovka and Khotimsk, to name a few — but places that were once the safe homes of bewildered children and their terrified parents. Occasionally, I wished that I knew more about Operation Barbarossa, but then I realized that, too, was the point: Survival, loss, horror occupied her subjects’ entire field of vision, not troop movements and victories.

In nearly every entry, “Mama and Papa” are invoked, the center of a child’s universe, fierce protectors and symbols of something resembling security in a world that has become a hellscape. Of course, many parents die. Some are shot in front of their children. Others disappear and never return. Some are burned to death in cottages that Germans torch. Still others are deported to concentration camps, because some of these were Jewish communities. The stories are marked by extraordinarily intimate details. A pregnant cousin of Vera Novikova, who is now a tramway dispatcher, was hanged, and witnesses, the children, were forbidden to cry or they would be shot. Dressmaker Polia Pashkevich, who was 4 years old when the war began, saw her mother “shot down in the street. When she fell, her overcoat opened, it became red, and the snow around mama became red.”

Finally Polia ended up in an orphanage. The war was over, and children would wait for their parents to take them home. When an unknown adult appeared, they would compete with one another. “My papa … My Mama …” “No, it’s my papa!” “They came to take me!” “No it’s me they’ll take!”

Then there are those who acknowledge the damage their childhood inflicted on their adult selves. Yura Karpovich, who is now a driver and was 8 years old when the war began, confesses, after recounting horrific details of murder and torture: “And I was little … I grew up with this. . . . I grew up gloomy and mistrustful, I have a difficult character. . . . It’s hard to love me.” And then he says: “Now I want to ask: Did God watch this? And what did He think?”

Why read a book of such unremitting misery? More to the point, why is a book of such unremitting misery so compulsively readable? We meet these children only once, and then we meet the next one, and the next one, and the next one. The narrative through-lines are suffering and wartime atrocities, not plot and character. But somehow it is impossible not to turn the page, impossible not to wonder whom we next might meet, impossible not to think differently about children caught in conflict. It has always been obvious that the lucky ones grow up to be adults. What is less obvious is that over time, we will reach the point when, as Valya Brinskaya, who was 12 and is now an engineer, notes: “We are the last witnesses. Our time is ending. We must speak. . . . Our words will be the last.” And having those words recorded matters.

Last Witnesses

An Oral History of the Children of World War II

By Svetlana Alexievich

Random House. 295 pp. $30