At the end of World War II, Soviet troops imprisoned hundreds of thousands of Japanese soldiers and civilians in Asia, sending them to labor camps in Siberia. Tens of thousands subsequently died in brutal conditions.

Although that dark historical episode has been written about in Japan, in Russia it has received little attention.

Last year, however, Russian scholar Sergey I. Kuznetsov published a book in Japanese that covers the subject in detail and condemns the Soviet authorities for the mass internment.

"Even the Soviet people hated those places," he said in a recent interview with Kyodo News. "There is no way to justify the consequent deaths of the tens of thousands of Japanese military prisoners there."

Many of the former prisoners have written or spoken of their ordeal. However, Kuznetsov's book is unique, as it marks the first time a Russian has produced a thorough review of the subject.

The university professor spent five years researching the topic, obtaining materials under Russia's new freedom of information measures, and then another five years writing the book.

First published in Russia, the Japanese version was put out by Shueisha Inc. under the title "Siberia no Nihonjin Horyotachi" ("The Japanese Prisoners of Siberia").

"By themselves, each of the facts are very insignificant. Yet when I strung them altogether, it turned into a grand piece of work," Kuznetsov said.

The book covers numerous dimensions of the internment program, such as the prison camps' locations and the communist indoctrination the inmates underwent.

Kuznetsov said the Soviet Interior Ministry deliberately destroyed many of the prisoners' graves, despite extensive efforts by the Japanese government to locate them.

Kuznetsov, 44, teaches Japanese history at Irkutsk University in his hometown of Irkutsk, southern Siberia. He said he was "naturally" drawn to the subject, even though few Russians have ever expressed outrage over it.

"My job is to let ordinary people know about the history of both countries," he said. "Doing so can help deepen ties between Japan and Russia."

Perhaps not surprisingly, the book has received emotional reactions from readers in Japan. Kuznetsov said he has received letters from former POWs asking for details about the locations of graveyards and the identities of those buried.

"One old person told me there was no way he could tell his family about what went on in Siberia," he said. "For the Russians, it is a long-forgotten story. But the people of Japan to this day continue to have sad memories."

Kuznetsov enjoys his weekends at his cottage doing carpentry as a hobby. His next book, which he has begun researching, will be about Russians who explored Japan in the 18th and 19th centuries, although he said writing it is "still a long way off."