Japanese soldiers and their service dogs wear gas masks during a training session, ca. 1933

Bunny Island: Japan and Chemical Weapons

How Japan's most secretive and deadly island turned into the cutest.

Japanese soldiers and their service dogs wear gas masks during a training session, ca. 1933

A short ferry ride away from mainland Japan, situated in the East/Inland Sea lies an island with a dark history. Leading up to the Sino-Japanese War the island hosted a secret manufacturing facility for the production and testing of chemical weapons. 

Today, the island is better known as Usaga Jima or Rabbit Island, made famous by the wild colony of rabbits who roam there freely delighting scores of tourists.

The chemical weapons program was top secret, and the island was immediately erased from all maps of Japan that were made after 1929.

The origins of the bunnies on the island also remains a mystery. One theory is that the poisonous gas produced on the island was tested on their ancestors. However, that theory has not been officially confirmed. 

The extent of the Japanese chemical weapons program became known at the end of World War Two through a series of interrogations of high-ranking military officials by US intelligence.

It was revealed that the chemical warfare policy allowed the use of chemical weapons in China but not in the Pacific Theatre against the Allies due to the former not having the ability to retaliate in the same way. The Japanese believed that the Americans on the other hand with their national industrial capacity could retaliate on a much greater scale.  

Finding chemical warfare morally horrifying, President Franklin D. Roosevelt shunned their use. In practice, the Americans only developed the capacity to engage in widescale chemical warfare towards the end of World War Two, at which point nuclear bombs made the question of chemical weapons obsolete.

The Battle of Shanghai, also known as the Battle of Songhu 1937. (Picture: Alamy)

The 1925 Geneva Protocol prohibited the use of chemical and biological weapons in war. However, since the end of the First World War, chemical weapons have taken the lives of more than a million people globally.

The first of its kind, the protocol had major drawbacks. It did not ban the production or stockpiling of gas or chemical weapons. A conciliatory ‘just in case’ clause enticed the major players who used poisonous gas in the Great War to sign, namely Germany, Britain, Austria, Russia, and France.  

The Land of the Rising Sun did not sign the 1925 Geneva Protocol. In 1929, Japan embarked on its chemical weapons program and by 1945 they had produced more than 6,000 tons of poisonous gas.

The production took place on Okunoshima, a small island off the coast of Hiroshima, measuring 800m in width.  

It was chosen for its secluded location away from civilian populations. In May 1929, the Okunoshima facility began production of tear and mustard gases but would later produce a myriad of other lethal gases such as phosgene.

Bunnies against the backdrop of an abandoned power plant on Okunoshima island. (Picture: Addy Cameron-Huff)

From 1937 to 1945, Japan used chemical weapons on as many as 2091 separate occasions, primarily in China. Estimates of casualties range from 36,968 to 80,000, including both military personnel and civilians. 

As the first shots of the war in China were fired during the Marco Polo Bridge Incident on 7 July 1937, the Japanese army began to use chemical weapons against the Chinese almost immediately. 

The first reported incident was as early as 18 July 1937. 

One of the worst occasions, when the gas was used, was during the ‘Ichang Incident’. During the battle that lasted three days, the Japanese army bombarded the Chinese with gas shells for almost five hours, dropping more than 300 gas bombs.  

The Chinese military, being technologically inferior to the Japanese Imperial Army, had no way of retaliating and lacked even basic protective equipment. Few soldiers were issued with gas masks and the ones that had them lacked the training to use them properly. 

Japan knew China did not have the capability to retaliate with chemical weapons. The same was not true of the United States. On 5 Junes 1942, President Franklin D. Roosevelt publicly warned Japan:

"I desire to make it unmistakably clear that if Japan persists in this inhuman form of warfare against China or against any other of the United Nations, such action will be regarded by this Government as though taken against the United States and retaliation in kind and in full measure will be meted out."

The warning worked, as confessed by General Akiyama Kinsei, who served as the director of the Chemical Weapons training school at Narashino from 1935 to 1940. During interrogation, he said that Roosevelt's warning of mass-scale retaliation prevented the Japanese from employing chemical warfare against the Allies in the Pacific Theatre.

A fluffle on Okunoshima island (Picture: Addy Cameron-Huff)

Today, the island once famous for the production of horrific deadly weapons is a tourist hotspot. While there is a ‘Poison Gas Museum’ that outlines the atrocities that were committed (mostly in China) with the weapons that were manufactured there, most people come for a different reason.

The island is overrun by friendly feral bunnies. 

A theory suggests that the rabbits are the descendants of the animals that were experimented on during the time that Okunoshima was an active facility for the production of poisonous gases.

However, the official line claims the animals that were used for experimentation were culled when the facility was shut down.  

Another theory is that eight rabbits were bought onto the island by school children who were no longer able to take care of them.  

Since cats and dogs are prohibited on the island and without any natural predators, the fluffle (the official name for a colony of bunnies) bred like … rabbits. Today, there are thousands of them hopping around the island, enjoying the attention of tourists – which during high season can also number thousands.  

The rebranding of the island’s image, whether unintentional or not, is in line with the rest of the county’s push towards being seen as a pop-culture superpower of all things cute and fantasy – an intentional move away from Japan’s old reputation of a fearsome militaristic state.

While there may be a lot of disparaging theories on how the rabbits got onto the island, few could deny that they are cute, or ‘kawaii’ in Japanese.

Cover image: Japanese soldiers and their service dogs wear gas masks during a training session 1933 (Picture: Alamy)