It was a remarkable discovery.

In 2001, while in London, German historian Sonke Neitzel stumbled upon a thick bundle of files at the British National Archives that offered new insights into the mindset of German soldiers who had fought during World War II.

Neitzel, a University of Glasgow faculty member, was familiar with reports pertaining to interrogations of German prisoners of war, particularly U-boat crewmen. But he had never heard of a covert program in which the Allies had secretly recorded the conversations of German POWs.

Yet that’s precisely what he found while reading some 800 pages of meticulously transcribed conversations of about 14,000 German soldiers who had been covertly bugged by the British and Americans.

“I was electrified,” he said.

The transcriptions were declassified in 1996, but no one recognized their historical value until Neitzel appeared.

Shortly afterward, he discovered that the National Archives in Washington, D.C., held an even larger collection of such material.

Teaming up with German social psychologist Harald Welzer, Neitzel has written a book that draws a chilling and definitive portrait of the soldiers who served in the Wehrmacht, the German army, during the war.

Originally published in German, Soldaten: On Fighting, Killing and Dying (McClelland & Stewart) was released on Sept. 25.

As Neitzel said in a recent interview, it offers empirical proof that the Wehrmacht under Adolf Hitler’s overall command was a “criminal organization.”

By his estimate, the Wehrmacht murdered about 20,000 Jews in the former Soviet Union and supported Einzatzgruppen units in the killing of more than one million Russian, Ukrainian and Baltic Jews.

In addition, he noted, Wehrmacht soldiers killed some 20,000 Jews in Poland and other Nazi-occupied countries.

“The [transcripts] make it clear that practically all German soldiers knew or suspected that Jews were being murdered en masse,” the authors write in Soldaten.

The supposition that Germany’s army fought a “clean” war was exploded by a 1990s exhibition in Germany, Crimes of the Wehrmacht, which sparked a nation-wide debate.

Compiled by the Hamburg Institute for Social Research, it’s widely regarded as having marked the end of the myth that the Wehrmacht emerged from the war with its hands unsoiled.

Neitzel, 44, says the Wehrmacht participated in the murder of Jews as executioners, witnesses, accomplices and support workers. Only on very rare occasions did Wehrmacht officers intervene to stop atrocities.

Soldiers in the Wehrmacht, having been bombarded by Nazi state propaganda that depicted Jews as outsiders and even sub-humans, had grown accustomed to regarding them as the enemy.

Although most Germans supported the regime’s antisemitic laws and applauded the forced emigration of German Jews, German soldiers on the front lines viewed the murder of Jews as something bad, a line that had been crossed and a shameful blot on German history, said Neitzel, editor of the academic journal German History in the 20th Century.

And yet, some soldiers in the 17-million-strong Wehrmacht proved to be heartless, cold-blooded killers.

Murdering Jews gave them something of a vicarious thrill. “They had the power of life and death,” said Neitzel, whose late father, born in 1930, was a true believer in the Nazi system. “You do it because you can do it.”

In Soldaten, the authors write, “Soldiers were only interested in carrying out their tasks, not questioning them.”

At the end of the day, Neitzel agreed, the crimes against humanity these soldiers committed in Germany’s name are a devastating commentary on the enduring consistency of human nature.

“It’s a big illusion to think that ‘clean’ wars can be waged. Atrocities in wars are unavoidable.” In wartime conditions, he added, mass violence, including rapes, is common. “The banality of war is astonishing. Future wars will be no different.”

The transcripts laid bare the attitudes of soldiers, who came from all walks of life and regions, and represented a rainbow of political convictions.

“The sample is not representative in a statistical sense, but gives the richest picture of the mentalities of soldiers ever recorded,” he said.

By his estimate, only 0.3 per cent of the transcripts refer to Jews, but they speak volumes.

As he and Welzer write, “Many of [the soldiers] are antisemites, but that is not identical with being Nazis. Nor does antisemitism have anything to do with willingness to kill.

A substantial number of the soldiers hate ‘the Jews,’ but are shocked at the mass executions [of Jews] by firing squads. Some are clear anti-Nazis, but support the anti-Jewish policies of Hitler’s regime.”

They add: “Most of the soldiers are scarcely interested in ideology, politics, world orders, and anything of that nature. They wage war not out of conviction, but because they are soldiers and fighting is their job.”

The majority of Wehrmacht soldiers had what is perhaps a unique definition of war crimes, defining them as the murder of women, children and POWs. And yet German troops killed upward of 3.3 million Soviet POWs, not to mention Jewish civilians, he said.

Neitzel maintains that virtually every German civilian adult was at least dimly aware of the Holocaust, though their knowledge of the telling details was limited.

“They knew that Jews were being put on trains bound for the east, and that they were not coming back.”

Germans obtained their information from soldiers, railway workers and bureaucrats. “There were a lot of rumours.”

Long before Crimes of the Wehrmacht startled Germans, scholars such as Neitzel were keenly aware that the Wehrmacht had compromised itself. Nonetheless, the German edition of Soldaten angered some Germans.

“We were accused of being traitors,” he recalled.

Their detractors, primarily right-wing Germans, claimed the Allied transcripts were rank forgeries.