The Imperial Japanese military used money to cover up its use of sex slaves on Bali during the war, a group of researchers from Kanto Gakuin University has said, citing a document found at the National Archives of Japan.

A Japanese chief warrant officer stationed on the Indonesian island during the war told a Justice Ministry investigation in August 1962 that he brought about 70 women to the military brothels.

According to the document, about 200 more women were also taken to the brothels.

He also said he was given about ¥700,000 to use to appease local residents. The officer said using money worked really well and there was not one complaint related to sex slavery.

The former Imperial Japanese Navy officer also said that what he feared most was the existence of these wartime brothels becoming known, the archive showed.

The document was found by a university group led by Hirofumi Hayashi, a professor of modern Japanese history.

“It is important as it confirms the military’s role mentioned in the Kono statement,” Hayashi said, referring to an official apology over wartime sex slavery made in 1993 by then-Chief Cabinet Secretary Yohei Kono.

Kono acknowledged the military’s role in coercing women — known euphemistically as “comfort women” — to provide sex for its soldiers before and during World War II.

The document was produced as part of a Justice Ministry investigation conducted to collect information in connection with war crime trials.

In November, Hayashi revealed he had found trial documents at the national archives relating to six cases heard before tribunals set up for Class-B and Class-C war criminals after the end of the war by China’s Nationalist Party and the Netherlands, then the colonial ruler of the Dutch East Indies (present-day Indonesia).

The materials had been kept by the Justice Ministry, but were transferred to the archives in 1999 or later.