Unit 731: Japan’s most lethal weapons program

WorldPolitics
20 Jun 2026 • 12:03 AM MYT
The Manila Times
The Manila Times

One of the longest-running English broadsheets in the Philippines

Unit 731: Japan’s most lethal weapons program

UNSTOPPABLE is how Japan’s so-called remilitarization is described by a growing sector of geopolitical analysts.

Beijing and some Southeast Asian nations regard Japan’s record defense budgets (2 percent of GDP) and liberal policies on arms export as threatening regional peace.

According to some analyses, Japan is transitioning to “neo-militarism,” which uses bureaucratic and legislative frameworks rather than the archaic military junta. For this reason, there is a growing call by radical Japanese to alter the pacifist Article 9 of Japan’s constitution. This issue was amplified when Japanese premier Sanae Takaichi declared sometime ago that Japan will have to be involved militarily in the event Taiwan is attacked, the assailant necessarily being implied as China. That statement triggered a groundswell of angry protests from Chinese officials.

Interestingly, Takaichi stuck to her words and refused to apologize. This has the demarcation line in the unresolved historic China-Japan animosity been impliedly restored.

It is under this revived antagonism that information suddenly surfaced in the media on a decadeslong Japanese war secret, Unit 731.

Quite a number of videos have been shown on social media detailing how from the start of World War II, Japan had embarked on what war experts consider as the world’s most lethal weapons program.

That was even long before America’s Manhattan Project which developed the first-ever atomic bomb late in World War II.

Below follows a detailed integration of the relevant information culled from a variety of videos on Unit 731.

During World War II, the Japanese Imperial Army operated one of the most lethal and expansive covert biological and chemical weapons programs in human history. Spearheaded primarily by Unit 731 under the command of General Shirō Ishii, this state-sponsored program resulted in the deaths of hundreds of thousands of people through horrific human experimentation and direct field deployment in occupied territories.

Official cover of the operation was the Epidemic Prevention and Water Purification Department. Its primary hub was headquartered in the Pingfang district of Harbin, Manchukuo (now Northeast China). The scale of operation was so massive, comprising facilities with multiple branches spanning mainland China and Southeast Asia.

Gen. Shirō Ishii, a medical officer in the Japanese Imperial Army, was among Japan’s top microbiologists.

The general activity of the project consisted of:

Horrific human experimentation to develop effective biochemical delivery systems; Japanese scientists used captive Chinese civilians, Russian dissidents, Korean prisoners and Allied prisoners of war as live test subjects, colloquially referring to them as “maruta” (logs). They were deliberately infected with deadly pathogens like bubonic plague, anthrax, cholera, typhoid and dysentery.

Vivisections, at which scientists performed agonizing surgical dissections on live, conscious patients without anesthesia to study the rapid progression of diseases on organs.

Environmental trauma, achieved by subjecting prisoners to forced frostbite, high-pressure chambers and chemical poisoning to analyze human survival thresholds.

Through those activities, at least 3,000 people died directly inside the Harbin facility, with no documented survivors among the test subjects.

In terms of deployment and weapon systems, the Japanese Imperial Army was on record as having deployed the following weapons aggressively in military campaigns:

Ceramic plague bombs, specialized clay/ceramic bombs (Uji bombs) filled with millions of plague-infected fleas. When detonated at low altitudes, the porcelain shell shattered without killing the insects.

Pathogens dispersed via low-flying aircraft sprays contaminated local water wells, livestock and food provisions in Chinese towns.

Blister agents (mustard gas), asphyxiants (phosgene) and blood agents (cyanogen chloride) used against Chinese troops and civilians.

Biological and chemical field strikes killed an estimated 200,000 to 300,000 Chinese civilians.

One significant but aborted operation was the Operation Cherry Blossoms at Night, an August 1945 suicide mission to attack Southern California with plague-infected fleas using submarine-launched planes. This was preempted by Japan’s surrender.

It is said that as defeat loomed in 1945, Ishii ordered the demolition of the research facilities and the execution of remaining prisoners to erase all physical evidence.

This was in compliance with a secret deal with Gen. Douglas MacArthur and the United States government granting Ishii and his top scientists complete immunity from war crimes prosecution.

In return for immunity, the Japanese scientists handed over volumes of human data, medical charts and testing records to supplement the American biological defense program.

As a result, many prominent members of Unit 731 went on to lead successful postwar careers in mainstream Japanese medicine, pharmaceutical corporations and academia.

Meantime, millions of decaying chemical shells were buried or thrown into rivers across China during the frantic 1945 retreat, creating an ongoing environmental hazard. Under the Chemical Weapons Convention, joint Sino-Japanese task forces work continuously to this day excavating and safely destroying the abandoned munitions.

Contemporary Japan has explicitly renounced all biochemical weapons, ratifying the Biological Weapons Convention in 1982 and the Chemical Weapons Convention in 1995.

In 1995, the domestic doomsday cult Aum Shinrikyo produced biological toxins and successfully executed a deadly nerve agent attack using sarin gas on the Tokyo subway system.

The attack resulted in 14 killed and 5,000 sickened.

So, Japan’s capacity for biochemical warfare — rated as the most lethal in the world — hasn’t waned.

And as we have shown, most of the scientists under Unit 731 have merged with civil society, pursuing legitimate callings.

What if Shoko Asahara, who orchestrated the Tokyo subway sarin attack was one of them? Who else could be in his mold as to start another Unit 731 in these times when the US-China conflict in the Asia-Pacific is escalating — with Japan, this time, unreservedly taking the US side.

Studying the areas covered by the wartime Unit 731, a Filipino heaves a sigh of relief, finding the Philippines not one of them.

But world alliances have been shifting sands since then. Japan, which used to be the US’ nemesis, is now its staunch ally, hence also of the Philippines, whose alliance with America remains unquestioned. Realizing this, that same Filipino shudders at the great prospect of his country inescapably being an accomplice of Japan in the event of one more operation by Unit 731.

And besides, haven’t all the facilities of Unit 731 been turned over to America in return for the guarantee to Ishii of immunity from prosecution for war crimes?

Those facilities for biochemical weapons production could be intact to this day — in fact, even improved to a more modern mode of production of biochemical weapons.

In 2003, the US embarked on a war against Iraq purportedly to confiscate its biochemical weapons of mass destruction. At war’s end, which saw massive destruction of Iraq’s military infrastructure and the execution of Iraqi President Saddam Hussein, no such biochemical weapons were found.

How could the US have thought of how massively lethal such a weapon would be if it had not had it yet in the first place?

Now we’re into this unmistakable shift of Japan back to its past glory as a military might.

There is no guarantee that in such a shift, Japan would not resort to Unit 731 again.

What atrocities against humanity the Philippines could be part of therefore in the event Unit 731 is activated one more time against China?

God forbid.

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