Unit 731: The War Criminals the U.S. Chose Not to Prosecute

The Story

Some of the darkest chapters of World War II took place far from Europe. In Japanese-occupied Manchuria, an army medical unit known as Unit 731 ran a secret biological weapons program that used prisoners as test subjects. The Los Angeles Times reported in 1988 that more than 3,000 Chinese and Russian prisoners died at the camp, and historians say villagers nearby were also killed.

The unit was established in 1936 near the city of Harbin under army doctor Shiro Ishii. Its activities have been documented by historians, by testimony from former members and by records later released in Japan, Russia and the United States. We will not detail the experiments here. It is enough to say they were lethal and carried out on people who had no choice.

"The fact is, we made a joint decision not to prosecute." (U.S. Army spokesman Norman M. Covert, Los Angeles Times, 1988)

The conspiracy theory concerns what happened next. After Japan surrendered in 1945, the United States occupied the country. Unit 731's leaders were not charged at the Tokyo war crimes tribunal. For decades, people asked why.

The answer began to emerge in the early 1980s. An October 1981 article by writer John W. Powell in the Bulletin of the Atomic Scientists used U.S. records to argue that American officials had protected Ishii's group. In December 1988 the Los Angeles Times reported on declassified memos that made the point directly.

One 1947 memo from the State-War-Navy Coordinating Committee, quoted by the Times, said protecting Ishii and his associates from war crimes prosecution would be "equivalent to an agreement that this government will not prosecute" them. The Times reported that U.S. officials valued the group's data and wanted to keep it away from the Soviet Union.

In response to research by historian Sheldon Harris, the U.S. Army confirmed the basic facts. Norman M. Covert, an Army spokesman at Fort Detrick, told the paper: "The fact is, we made a joint decision not to prosecute." The goal, he said, was to keep the information out of Soviet hands. He added: "The U.S. government and I will never say that a deal was made . . . but it can be interpreted that way."

That nuance is where historians still disagree. Some describe a clear immunity arrangement. Others, such as Army historian Edward J. Drea, quoted in the same 1988 article, have argued that U.S. prosecutors also lacked enough evidence to bring a case. Either way, the result was the same: no Unit 731 leader faced an American-backed trial.

The Soviet Union took a different path, trying a group of captured Japanese personnel involved in biological warfare at Khabarovsk in 1949. Many in the West dismissed those trials as propaganda at the time.

More U.S. records were declassified after Congress passed the Japanese Imperial Government Disclosure Act in 2000. The National Archives' Interagency Working Group oversaw the release and published its final report in 2007.

So the core claim stands. A secret decision was made to let men responsible for deadly human experiments go untried, partly for their data. It was not a theory. It was policy, and it took decades to come out.