The Imperial Japanese Army tested cyanide gas on Australian and Dutch East Indies prisoners of war in 1944 in Indonesia’s Kai Islands, according to a document recently uncovered by a Japanese researcher.

Yoshiaki Yoshimi, a professor at Chuo University and an expert on modern Japanese history, discovered the document in the Australian national archives in Canberra. He said it is the first piece of evidence to detail Japan’s experiments on an Australian POW.

Some historians say the Japanese army had planned to use cyanide gas as a last resort in fighting against the Allies.

The Japanese army’s Unit 731 is widely known for experimenting on Chinese in northeastern China with germs and chemical weapons during World War II.

Yoshimi obtained the document with the help of Toshiyuki Tanaka, a professor at Hiroshima City University, and has included the finding in his latest book on Japan’s gas warfare, to be published Wednesday.

The 400-page document is a compilation of records on trials of Japanese war criminals by the Australian military held in Hong Kong on July 15, 1948, three years after the end of the war. It includes the ruling written in English and confessions in Japanese.

In November 1944, according to the document, a lieutenant in charge of poison gas at the No. 5 Division of the army threw bottles of cyanide gas on an Australian air force captain and a sergeant of the Dutch East Indies air force. The gas was designed for antitank warfare.

The division’s lieutenant colonel had ordered the lieutenant to test the effectiveness of the gas, the document says.

After the POWs collapsed, Japanese military police stabbed them to death with bayonets. The lieutenant and the lieutenant colonel were sentenced to death by hanging by the military tribunal, according to the document.

A deposition by the lieutenant, dated April 17, 1947, says the chemical weapons were 4 years old at the time and showed signs of deterioration, prompting the Japanese to test their effectiveness.

The document quotes the lieutenant as saying he reported to his superiors that the gas was still effective.

At the time the alleged human experiments took place, the Allies were about to take over New Guinea Island, which was occupied by Japan, and were expected to advance to the Kai Islands.

The Japanese army had secretly engaged in chemical warfare — banned under international law — in China since shortly after the war there started in 1937.

In July 1944, the General Staff Office of the Japanese army, responding to a warning from U.S. authorities for a reprisal, issued an order for banning the use of poison gas by the army.

But the disclosed records show that such orders were not heeded among officers on the battle fronts facing the prospect of imminent enemy offensives.

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