Reviewed on July 7, 2015, by Roger Cohen, The New York Times

Of an estimated 2.3 million prisoners who entered the hell of the Nazi concentration camps, over 1.7 million were killed, whether gassed or worked to their skeletal ends. Many went straight to their deaths, including about 870,000 Jews murdered on arrival and without registration at Auschwitz; others endured a slower annihilation, reduced to what Hannah Arendt called “ghastly marionettes with human faces.” Millions more were killed in other ways, but there were also survivors, and at the end of “KL: A History of the Nazi Concentration Camps,” his monumental study of the SS camps, Nikolaus Wachsmann focuses on one. His name is Moritz Choinowski, a Polish-born Jew detained by the Gestapo in 1939 in the German town of Magdeburg. By the time of his liberation on April 29, 1945, Choinow­ski has survived Buchenwald, Auschwitz, a slowly growing German camp called Gross-Rosen and finally Dachau, as well as the nightmarish forms of transportation between them. “Is this possible?” he sobs in the Dachau infirmary. It was, just.

Through his atrocious odyssey, Choinowski experienced the various degrees of Nazi depravity under Hitler. There were gradations of horror. The camps evolved as Hitler’s regime threw off every last constraint in the maelstrom of all-out war. They were not monolithic. One of the merits of “KL” (a common abbreviation of Konzentrationslager, or concentration camp) is the way it captures the inexorable slide, over a 12-year arc, from fierce repression and cruelty to systematic murder and industrialized extermination. As Wachsmann writes: “In a radical totalitarian state like the Third Reich, terror did not decrease after the regime established itself. Nazi leaders pursued ever more extreme aims, and so the KL expanded, even as domestic political opposition diminished.”

Dachau in 1933 — when it was established near Munich as the first of what would become 27 main SS camps — and Auschwitz in 1944 were utterly distinct. Yet they belonged to the same lawless universe. Dachau, at the outset, targeted political opponents of the Nazis, often Communists, subjecting them to harsh imprisonment and occasionally capricious murder. Auschwitz, by the penultimate year of the war, was a sprawling death complex, its gas chambers filled with the screams of the dying, its crematoriums smoking endlessly: a flesh-fed destruction line for European Jewry, Gypsies and others. As Primo Levi would put it, “Trains heavily laden with human beings went in each day, and all that came out was the ashes of their bodies, their hair, the gold of their teeth.” In this descent to the nadir of human iniquity the camp, in all its forms, was central. Wachsmann writes, “The concentration camps embodied the spirit of Nazism like no other institution in the Third Reich.”

That spirit emanated ultimately from Hitler himself through his chosen chief henchman, the SS leader Heinrich Himmler, “the undisputed master of the Third Reich terror machine,” who became chief of police in 1936. It was sustained by a corps of SS lifers of strikingly similar backgrounds — born around the turn of the 20th century, shaped by the humiliation of German defeat in World War I, radicalized by the paramilitary struggle against the Weimar Republic and at last let loose to indulge every sadistic fantasy (as well as enjoy the considerable perks of their posts, like the swimming pool and tennis courts at Dachau). Their modus operandi was well captured by one SS officer, Hans Loritz, who, when he took over the Esterwegen camp in 1934, declared: “In regards to discipline, I am a swine.”

Typical was Rudolf Höss. He was born in 1900 (the same year as Himmler), wounded in the war, recruited to the SS in 1933, became a Dachau sentry in 1934, was promoted to officer rank (Untersturmführer) in 1936, moved to Sachsenhausen in 1938, before rising in 1940 to become commandant at Auschwitz, where, as he put it in his memoir, “Every wish of my wife, of my children, was met.” His family lived in a large villa, and Frau Höss had a retinue of female prisoners working as tailors and hairdressers. Once absolute power had been learned at the repressive level, it could readily be extended to the annihilationist level. The camps nourished their own, pushing their overseers to levels of brutality perhaps not even they had imagined at the outset.

Wachsmann, a history professor at London University’s Birkbeck College, has written a work of prodigious scholarship. At 865 pages, it is, in every sense, no light read. In fact it is claustrophobic in its evocation of the depths to which people can succumb. Readers may find themselves wanting out, but there is always worse to come. The book does not upend our understanding of the camp system, whose core elements are well known by now. But it imbues them with agonizing human texture and extraordinary detail. This is as relentless a chronicle of the collapse of an entire society and civilization — from its doctors drawn to every inhuman experiment to its foot soldiers looting the dead — as may be imagined.

Were the SS camps “typically German,” as some prisoners believed? Wachsmann answers that this “seems doubtful” in that “the men behind the KL system were far more invested in radical Nazi ideology than most ordinary Germans, who felt more ambivalent about the camps.” It is unclear what the evidence for this ambivalence is. He suggests that “the role of the camps in the Nazi Final Solution did not fully penetrate public consciousness.” Yet he himself demonstrates how integral to German racial designs, the German economy, German industry, German medical fantasies and German territorial expansionism the camps became. By the end of the war their myriad satellite industrial camps were everywhere, hard to ignore.

The SS camps were the expression of the Nazi ideology to which Germans, in their overwhelming majority, acquiesced. They existed to free Europe of Jews and other undesirables, lock in the Aryan master race, empty the east of its citizens for German Lebensraum and cow any resistance through systematic terror. For a dozen years, and with steady intensification, they did their foul work, mostly ignored by the Allies despite growing evidence of the Nazi genocide.

Many fascinating details emerge: the early clash between Himmler and Hermann Göring, who wanted to roll back the excesses of the camps; the first use of Zyklon B pellets in 1941 at Auschwitz for the killing of Soviet prisoners of war (“One could see that these people had scratched and bitten each other in a fit of madness before they died,” one witness observed); the links, moral and technical, between the early euthanasia programs in Germany and the mass gassings in Poland; how pleased Höss was that this method was less stressful for the SS than shootings — “all of us would be spared these blood baths”; the terrible corruptive force of terror and the fight to survive, evident in the Kapo system and even in the decision of some prison doctors at Auschwitz to kill newborn babies in order to save their mothers, who would otherwise have been murdered. It is sobering to reflect that three of the most murderous places — Belzec, Sobibor and Treblinka — do not fall within the scope of the book because, as death camps exclusively rather than also work camps, they were not part of the SS network, reporting to authorities in Lublin rather than Berlin.

One Olga Lengyel arrives in Auschwitz determined to protect her son from hard labor. She is asked by an SS physician (strange oxymoron), Dr. Fritz Klein, how old her son is. She says he is under 13, although he looks older. The boy is promptly sent to the gas. As Wachsmann writes, “Those under the age of 14 were almost all gassed on arrival.” After the war, Lengyel writes in despair, “How should I have known?” How indeed could anyone, so far had the Nazis gone in the application of the unthinkable.

Wachsmann makes the unimaginable palpable. That is his great achievement. It is therefore strange that he bitterly attacks the psychologist Bruno Bettelheim, a survivor of Dachau and Buchenwald, for saying the Jews of Europe had gone “like lemmings” to the gas. This, he writes, is “grievously wrong.” But the fact is a vast majority of Jews killed in the camps or shot dead in the forests put up scant resistance. They could not believe what was about to happen to them. Out of this unimaginable experience came the ­never-again Zionism that led to the creation in 1948 of the modern state of Israel.

To the last, Hitler and Himmler hounded the camps’ prisoners, trying to efface traces of the mass murder, driving them on death marches that took droves of emaciated Jews to Germany from Poland. The Allies could not believe what they found in Dachau, Bergen-Belsen, Buchenwald and elsewhere. To be frank, they had not really cared to pay much attention. Justice, inevitably, was imperfect. Quickly, Cold War imperatives took over from the quest for justice: West Germany was needed to fight Stalin. Germany slowly recovered and in the end was made whole.

The mystery remains. The Holocaust can never quite be digested, even when it is dissected into such minute detail. Buchenwald stood near Goethe’s hometown, Weimar. As Wachsmann writes, the connection with Goethe could not be severed: “A large oak tree, under which he had supposedly met with his muse, stood right on the new camp grounds; because it was protected, the SS had to build around it.”

They did and, step by step, Höss and his ilk found a way to usher Germany from the inspiration of its greatest writer to the inferno of mass murder.