Around 400 young Norwegians were employed from June 1942 to guard Serbian prisoners taken to camps in the north of the country, where they were used as slave labour to build roads and railroads.
"Some of them started behaving very brutally, resulting in a lot of killing, torture and violence in the camps in a very short time," Eirik Veum, the book's author, told The Local.
"The SS officers said,'hey guys, calm down, you're too violent, you're too brutal', and they took away their bayonets. After 10 months they were pulled from duty, because too many prisoners were killed."
Remarkably, the Yugoslavs who survived the camps said that their lives improved once the German guards took over.
"They said that once the Norwegians were taken out, things started to get a little bit more normal. They got more medicine, and They started
to be treated like humans not animals," Veum said. "It's interesting that the German SS guards were more humane than some of the Norwegians guards during the period they were on duty."
The guards were drawn from Hird, a paramilitary organization created by the Nasjonal Samling, Norway's Nazi movement, in 1933.
Once the Germans took control of Norway in April 1940, they drew on Hird's membership, employing them for example to round up Oslo's Jewish citizens, for which Hird members were paid 20 Norwegian kroner a night.
Veum has drawn most of his information from public records dating back to the the trials of collaborators which took place after Norway was liberated in 1945.
He says that although the information was not secret, it has caused controversy in Norway nonetheless.
"In Norway this is very emotional, because in our history of the war in Norway, we have been focusing on the resistance movement. We have been talking for 65 years about how brave the Norwegians were in fighting the Germans, but the part about all the Norwegians who were fighting for the Nazis, we've never talked about."
According to Veum, the young Hird prison guards, some of whom were only 15 years old, would torture the Serbian prisoners and shoot them on a whim.
"You also had torture which was very cruel. They would take rats and tie them by a rope to a prisoner, and when the rat got too hungry, it
would start to eat the prisoner to get free, through the body," Veum said.
One of the most notorious Hird guards, a man called Louis Tidemann Johansen, was reprimanded by the Germans for getting drunk, and then shooting prisoners almost as a sport.
Veum said that the book had come as a shock to many in Norway.
"All this kind of stuff has not been part of Norwegian war history. It hasn't been a secret, it hasn't been hidden. Some of historians know
about it, and some of the locals who lived by the camps knew about it."
The biggest controversy has come from his decision to name the members of Hird and detail the crimes they committed.
"Most criticism comes from historians in Norway, who don't like this kind of identifying, because it's not how we do it in Norway," he
"We had Johansen shooting prisoners when he was drunk up in the North. I find it interesting that we are discussing my decision to identify more than what actually happened, that Norwegians also played a part in the war crimes committed during World War II, and on a larger scale that we had been aware of."