The Imperial Japanese Army asked the government to provide one “comfort woman,” or ianfu in Japanese, for every 70 soldiers, according to documents reviewed by Kyodo News on Friday that shed new light on the wartime practice of forcing and coercing women into military brothels.

The documents were collected by the Cabinet Secretariat between April 2017 and March 2019. Of the 23 documents, 13 are classified dispatches from Japanese consulates in China to the Foreign Ministry in Tokyo dated 1938, the year after the Marco Polo Bridge Incident that sparked the Second Sino-Japanese War.

One dispatch from the consul general of Jinan to the foreign minister reports that the Japanese invasion had caused a surge in prostitution in the area, with a head count of 101 geisha from mainland Japan, 110 comfort women from mainland Japan, and 228 comfort women from the Korean Peninsula, which had been annexed in 1910.

The dispatch says that as Japanese forces had made further advances, “at least 500 comfort women must be concentrated here by the end of April.”

It also notes that 186 women had ridden south in military vehicles after the occupation of Xuzhou in Jiangsu province.

Another dispatch from the consul general of Qingdao in Shandong province notes that the Imperial Army had asked for one woman to accommodate every 70 soldiers, while the Navy had requested 150 more comfort women and geisha.

The documents lend weight to the landmark 1993 apology statement by then-Chief Cabinet Secretary Yohei Kono that accepted blame for the Japanese military’s involvement in recruiting comfort women, in many cases against their own will, and apologized to them.

Hirofumi Hayashi, a professor at Kanto Gakuin University, said the documents proved that “the military had an active hand in gathering women.”

“They were sounding out the Foreign Ministry through the consulates,” he said.

The exact number of comfort women remains unknown, with estimates ranging from 20,000 to hundreds of thousands. The women were recruited from mainland Japan, the Korean Peninsula, Taiwan and other countries.

The issue continues to be a source of friction between Japan and South Korea, with activists setting up statues symbolizing the victims at home and abroad in an effort to raise awareness.