Entomological Evil

Pingfan was an undistinguished cluster of eight or ten villages about 15 miles south of Harbin. That is, until the Japanese army made the residents sell their homes for a pittance, razed the hamlets, and forced 15,000 Chinese laborers to build Ishii's dream.1

When completed in 1939, the facility was a bizarre cross between a biomedical death camp and a resort spa. Within its two square miles, Pingfan comprised more than 150 structures: headquarters building (with a moat), administrative offices, laboratories, barns, greenhouses, a power station, a school, a brothel, recreational facilities (including a swimming pool), housing for 3,000 scientists, dormitories for technicians and soldiers—and a prison for the inmates, along with the requisite crematorium (see Figure 9.1).

Ishii had learned an important lesson from the escape fiasco at Zhang Ma, so Pingfan was surrounded by a 15-foot wall topped with high-voltage lines, barbed wire, and watchtowers. In a stroke of architectural paranoia, most of the new buildings within the facility were kept to one story so that they could not be seen from beyond the walls. The operation was further hidden by being named the "Anti-Epidemic Water Supply and Purification Bureau" but soon came to be known by its infamous moniker: Unit 731. Secrecy even trumped a sacrosanct tradition—while the entrance to Pingfan was devoid of symbols, all other Japanese installations displayed the imperial chrysanthemum on their front gates.

Despite these efforts, nobody could hope to conceal a facility of such magnitude. Needing a cover story, the Japanese told the local people that Pingfan had been converted into a lumber mill. From this absurd effort at deception arose the sickest humor, as the scientists of Unit 731 came to refer to their human subjects as maruta, meaning "logs."

Figure 9.1. Most of the Pingfan facility that housed Unit 731 was destroyed by the Japanese in an effort to cover up evidence of their biological and entomological warfare program and human experimentation. The ruins of the power plant remain as mute testimony to the enormous scale of research and development efforts—and the suffering and depravity that took place. (Photo by M. Ziegler)

While waiting for his demonic Shangri-la to be completed, Ishii played politics in Harbin, enjoying a life of luxury with his wife and seven children. His schmoozing paid off in the form of a phenomenal annual budget of 10 million yen (an office clerk, working 90 hours a week in Tokyo, earned five yen a month). Unit 731's budget would eventually rival that of the Manhattan Project in the United States.

Ishii and company occupied Pingfan in the fall of 1938. Staffing such an enormous facility was one of his most important administrative duties. There had been enough military doctors to support the relatively modest work at Zhang Ma, but Pingfan was an enormous facility. Ishii routinely spent three months a year in Japan, enticing top scientists with promises of unfettered research in unparalleled facilities and valued service to the nation. The military spawned Ishii's fiendish program, but it could never have flourished without the complicity of the medical and scientific communities.

The scope of Unit 731's work included toxins, plant pathogens, vaccines, and a gruesome range of projects for which human testing was deemed necessary, including studies of frostbite, high-altitude decompression, and poisonous gases. But the bread and butter of Ishii's research program was human disease: finding a microbe and a means of delivery that would constitute a lethal weapon system. Unit 731 initially adopted a shotgun approach. The list of pathogens known to have been tested reads like a who's who of human dis ease: from anthrax, brucellosis, and cholera to typhoid, venereal diseases, and whooping cough. Not satisfied with their own inventory, the Japanese tried to secure pathogens from other sources, including the Americans.

When Naito Ryoichi arrived in New York on February 29,1939, nobody was expecting him.2 However, he seemed to be a respectable scientist on a credible mission. An assistant professor at the Army Medical College in Tokyo, Naito presented a letter of introduction from the Japanese Embassy in Washington. The document explained that Naito was a medical researcher seeking samples of yellow fever virus for vaccine development. He was directed to the office of Dr. William A. Sawyer, director of the virus laboratories at the Rockefeller Institute of Medical Research.

Sawyer was immediately suspicious. Yellow fever had little potential to afflict Japan. Moreover, to prevent the spread of the disease, both the League of Nations and the Congress of Tropical Medicine had explicitly prohibited the importation of the virus into Asian countries for any reason. A Japanese scientist should have known about these restrictions, but Naito feigned naivete. Sawyer gave his regrets, sent Naito on his way, and wrongly assumed that the matter was closed.

Three days later, one of Sawyer's technicians was stopped on the street by "a man with a foreign accent." The man, almost surely Naito, offered the technician $1,000 for a sample of the Asibi strain of yellow fever—an extremely virulent form of the virus. The man explained that a professional rivalry kept Sawyer from providing the needed sample. When this appeal failed, the bribe was tripled. Becoming alarmed, the technician fled from the increasingly desperate man and reported the incident to the Rockefeller Institute. The information was passed to the State Department, where the strange event was dutifully filed. Although the incident caught the eye of the Army Surgeon General's office, the U.S. military had largely pooh-poohed biological warfare. Fortunately for the Japanese, the Americans were nearly as naive as Naito pretended to be.

Although unable to secure the most virulent strains of some diseases, the screening process at Pingfan soon narrowed the list of pathogens.3 Based on operational considerations and test results, the scientists in Unit 731 focused their studies on two agents deemed to have the greatest potential for weap-onization: cholera and plague. Early tests at Pingfan concentrated on various means of spreading bacteria via sprays and bombs. These direct approaches had the advantage of being simple, but the disadvantage of being ineffective. The animal and human subjects did not become infected at nearly the desired rate. However, wartime scientists rarely have the time to perfect their creations before they are deployed by the military.

In the summer of 1939, the Japanese engaged in their first major border clash with the Soviets. Skirmishes near the village of Nomonhan had rapidly escalated, and the Kwantung Army was getting thrashed. The precarious position of the Japanese was deteriorating and they needed a tactical advantage— some secret weapon that the better-equipped Russians lacked. So they called in Unit 731.4 Ishii saw the Halha River, which roughly divided the armies, as the key to his plan. He dispatched two teams of commandos, who paddled rubber rafts to the Soviet side of the river and poured six gallons of a salmonella and typhoid concentrate (not as promising as cholera, but worth a shot) into the water. His unit also provided the Kwantung Army with 2,000 warheads filled with plague bacteria for shelling the Russian troops. Unit 731 had fired its first biological shots of the war. But there is a big difference between shooting and hitting something.

Undeterred by the epidemiological evidence, Ishii presented the campaign as an unqualified triumph. As for the river assault, Ishii pointed to the Soviet losses to the waterborne diseases dysentery and cholera, while carefully avoiding the troublesome details: neither of the relevant pathogens was poured into the river, Japanese troops suffered similar losses to these diseases, and the only sure victims of the attack were the 40 Japanese who accidentally contracted typhoid fever in the course of handling the jugs of microbes. And the bacterial bombs? Ishii reported that plague had taken a toll on the Soviets at Nomonhan. Of course, there was no sense in his pointing out that the Japanese forces had been similarly sickened, which would suggest that either Unit 731's microbes had drifted back into the Japanese lines (not likely) or the biological attack had not inflicted disease on the enemy (very likely).

Ishii and his scientific staff fully understood that simply dumping pathogens into a moving river and exploding shells laden with bacteria were unlikely to trigger disease outbreaks. So why risk operational failure? In 1939, Unit 731 was on an upward trajectory but clever research would not impress the Japanese hierarchy. To build his empire, Ishii needed tangible results—such as a cleverly scripted battlefield drama. Nomonhan was the perfect stage, and Ishii knew that his audience was both clueless and desperate—clueless as to how to assess the performance of the microbial actors and desperate for any reason to cheer. When Ishii lit up the "Applause" sign for biological warfare, the Japanese leadership gave him a standing ovation. In 1940, Emperor Hirohito decreed a substantial increase in funding for Unit 731. But Ishii knew that his production had been a flop and directed his scientific staff to ensure that the next performance would be a legitimate blockbuster.

The researchers understood that biological warfare had run into two fundamental problems. First, human pathogens are well suited to living in host tissues but poorly adapted to living outside. Heat, cold, desiccation, and ultraviolet radiation quickly destroy the microbes. And second, bacteria cannot move in the environment. Following release from a spray nozzle or bomb casing, only an infinitesimal minority of microbes happen to drift passively into human contact. Even these fortunate few must be inhaled or ingested—and then avoid the host's immunological defenses. There had to be a more reliable delivery system.

The answer finally came to Ishii and his staff: they'd been too clever by half.5 Rather than forcing human ingenuity at every step of disease transmission, the key was to exploit what millions of years of evolution had painstakingly developed: vectors. Insects solved the problems that had confronted Unit 731 scientists. Fleas, flies, and their ilk protected fragile microbes from the harsh environment while carrying the bacteria directly to the target. And, as an added bonus, some vectors support microbial reproduction in their tissues, effectively amplifying the pathogenic payload.

Delivering infected insects to a military target, however, required genuine innovation. The initial approach was to fully mimic nature, releasing flea-infested rats behind enemy lines. The researchers packaged the animals in parachute-delivered paper containers.6 As an added twist, the containers self-ignited after releasing their contents, thereby destroying evidence of a biological attack. But the rodent payload required complicated handling and logistics that precluded large-scale attacks.

Eliminating the rats, the Japanese began to adapt an existing delivery sys-tem.7 The Uji bomb was originally conceived to carry a slurry of bacteria, and its ten-quart compartment could hold a lot of fleas (see Figure 9.2). But the high explosive used to rupture the steel casing and aerosolize the enclosed pathogens killed most of the insects. Glass casings were tried, but their fragility made loading a risky business. Then Ishii hit upon the perfect material.

Exploiting Japan's ceramic heritage, he commissioned village artisans to fashion bombshells. Never suspecting the payload of their ceramic containers, the craftsmen soon perfected the casings. At this point, Ishii standardized production and moved fabrication within the walls of Pingfan.

Early trials involved loading the ceramic bomb with 3,000 to 6,000 fleas, with a few rats aboard to provide an in-flight meal for the insects. The rats did

Figure 9.2. An Uji bomb designed by Japan's Unit 731 for carrying ten quarts of bacterial slurry. This basic design was modified to disperse thousands of plague-infected fleas over a target. The disease vectors were packed in small porcelain bulbs set within a ceramic bomb casing. A modest, timed charge exploded the ten-quart payload and thereby released fleas from an altitude of about 500 feet. These devices were used against Chinese targets, but the Japanese soon turned to direct spraying of fleas from airplanes. (Photo by M. Ziegler)

not survive the impact, which was fine, given that the fleas were supposed to be seeking human hosts. In any case, the rats were soon abandoned as they added extra weight, and the fleas did fine without a snack on the way to the target.

In the "new and improved" Uji bomb, the plague-infected fleas were packed into small porcelain bulbs set inside the larger bomb casing. When a modest charge exploded the casing, its fragments shattered the thin bulbs. With an effective delivery system in place, the next challenge was to produce pathogens and vectors in massive quantities.

Pharmaceutical companies and breweries served as the models for industrial-scale production of microbes. Despite some novel challenges (nobody worries if a few yeast cells escape from a keg of beer, but a vat of deadly bacteria is another matter), it was not long before Pingfan was culturing more than 1,500 pounds of microbes every month. Although microbial production methods were well known, nobody had mass-reared fleas.

Unit 731 developed increasingly effective methods for breeding enormous quantities of fleas.8 At first, the insects were simply produced using human hosts. Ishii's scientists housed a group of ten prisoners in an isolated shed. The men were dressed in heavily padded clothes and seeded with fleas. The human incubators were expected to meet their daily production quota by harvesting a hundred fleas. While 1,000 fleas a day might have been sufficient for research needs, this level of production could not meet the demands of an operational

weapon system. So the Japanese devised a process that yielded a phenomenal stockpile of infected vectors.

To start the production cycle, feral rats were caught and chloroformed, and boys were employed to pick fleas from the rodents. The insects were placed into test tubes that were then upended over the shaved bellies of anesthetized, plague-infected rats. Once the fleas had fed and acquired bacteria, the insects were transferred to incubators stocked with uninfected rodents and fleas. This method allowed the continuous production of infected vectors. So great was the demand for rodents to fuel the furious rate of insect production that a four-story granary (an exemption to the one-story constraint for secrecy) was built to feed and house the colony.

As each generation of fleas matured, semi-nude workers harvested and packaged the infected insects. By dressing in loin cloths, the men ensured that a flea landing on bare skin could be detected and brushed off before it had a chance to bite. Major General Kawashima Kiyoshi, a physician and chief of the Medical Service, described the scale of production:

In the detachment's 2nd Division there were specially-equipped premises capable of housing approximately 4,500 incubators. Three or four white mice were put through each incubator in the course of a month; these mice were held in the incubator by means of a special attachment device. There was a nutritive medium and several kinds of fleas in the incubator [both rat fleas and human fleas were produced]. The incubation period lasted three to four months, in the course of which each incubator yielded about ten grams of fleas. Thus, in three to four months the detachment bred about 45 kilograms [99 pounds] of fleas suitable for infection with plague.9

Given Kawashima's testimony and the fact that a kilogram of fleas consists of about 3 million individuals, at peak production the Japanese could produce more than half a billion plague-infected fleas per year. Such a biological capacity surely delighted Ishii, but he also needed to develop a psychological capacity among his scientists for inflicting suffering.

If Unit 731 was to refine entomological warfare, the researchers had to be desensitized to human suffering.10 After thousands of repetitions, the killing of animals becomes mundane. From here, one need only begin to speak, and then think, of humans as laboratory animals to callous the soul. In this way, the experiments at Pingfan eroded the vestiges of moral constraints among the scientists.

Within the walls of Pingfan, no structures had a more sinister purpose than the Ro and Ha buildings—the prisons that housed the human subjects.11 Each building was 120 feet long and 65 feet wide, with Ro dedicated to males and Ha containing both sexes, along with children and infants. The structures could house 400 prisoners, but they typically operated at half capacity. To obtain reliable experimental results, the prisoners were kept in decent conditions: the buildings had central heating and cooling, the cells had flush toilets, and the inmates were provided with nutritious food.

Most of the maruta were acquired from Harbin. Han Chinese were most numerous, but experimental subjects included Mongolians, Koreans, White Russians, and Jews. From a processing center in the city, they were transported to Pingfan in freight cars or trucks, deposited at the facility's administrative building, and given numbers. The Japanese assigned code numbers up to 1,500 and then began over again. This allowed sufficient differentiation for purposes of scientific record keeping but confused any attempt to determine the fate of an individual or reconstruct the extent of experimentation. Despite the coding system, it is evident that from 1940 to 1945, the researchers at Pingfan used at least 600 human subjects per year, and some estimates put the number closer to 2,000. What is certain is that nobody who left the administrative center via an underground tunnel to either the Ro or Ha building lived to tell the tale (see Figure 9.3).

Figure 9.3. The former administrative building at Pingfan now houses a museum with dioramas, artifacts, and other displays of the work done by Unit 731. Although thousands of people died within the walls of the facility, the Japanese used an ambiguous numbering system to make it extremely difficult to trace individual prisoners. Only 277 names are known today, and these are engraved on this memorial. (Photo by M. Ziegler)

Human subjects were the key to the rapid development of biological weapons at Pingfan. Various modes of infection were tested—injection, inhalation, contact wounds, contaminated shrapnel—but nothing was more promising than plague-infected fleas. A postwar report based on interviews with Unit 731 scientists detailed the findings of particular experiments:

The fleas were mixed with sand before being filled into the bomb. About 80 percent of fleas survived the explosion which was carried out in a 10-meter square chamber. . . . Eight of the 10 subjects received flea bites and became infected and 6 of the 8 died.12

The most heinous aspect of this research came from the medical scientists' compulsion to precisely monitor the course of infection, an infatuation that led to the practice of vivisecting human subjects. The bizarre rationale was offered by one of the medical technicians—along with a graphic account of the process:

The results of the effects of infection cannot be obtained accurately once a person dies because putrefactive bacteria set in. Putrefactive bacteria are stronger than plague germs. So, for obtaining accurate results, it is important whether the subject is alive or not. . . . As soon as the symptoms were observed, the prisoner was taken from his cell and into the dissection room. He was stripped and placed on the table, screaming, trying to fight back. He was strapped down, still screaming frightfully. One of the doctors stuffed a towel in his mouth, then with one quick slice of the scalpel he was opened up.13

The scientists considered the Chinese to be an inferior race but suitable as laboratory animals. Indeed, the racism of the Japanese was global in scope, stretching to include Americans and Europeans. In previous times, military honor would have stood between POW camps and Unit 731, but Ishii convinced his underlings to extend their studies of human subjects to "white rats."

The POW camp at Mukden was 300 miles southwest of Pingfan.14 With the war in the Pacific intensifying, the Japanese fully expected to use biological weapons against Caucasian troops, and the scientists thought it important to determine if soldiers of European descent would respond differently to the pathogens. Although the nature and extent of experiments remain matters of debate, the best estimates place the number of POWs used as guinea pigs between 200 and 1,500. Americans seem to have been the principal subjects of experimentation, although British, Australian, New Zealand, and Dutch prisoners were also used. In a particularly gruesome move, a Japanese scientist announced his plan to use a portion of liver excised from an American POW to develop a poisonous bait for bed bugs (family Cimicidae). We may never be certain how many POWs were converted into laboratory animals, but we can be sure that knowledge of human experimentation extended far beyond the walls of Pingfan (see Figure 9.4).

Ishii was eager to reveal his work to his superiors.15 Films of human experiments were screened by high-ranking officers, but Ishii needed support beyond the military. So he proudly showed his documentary to the prime minister, Prince Takeda (Hirohito's cousin), and Prince Mikasa (the emperor's youngest brother). There can be little doubt that Hirohito himself knew that human experimentation was ongoing in Manchuria. And Unit 731's "open secret" extended beyond the halls of the military and government—Japan's scientific community was fully aware of the research being conducted at Pingfan.

Ishii gave regular presentations at army medical colleges, civilian universities, and scientific conferences. For those who missed his lectures, the nature

Figure 9.4. A rare photo documenting the work of Unit 731. Although no higher-quality version of the image exists, the photo is sufficient to show a doctor standing in front of a pile of bodies of Chinese prisoners who had been used as human guinea pigs. Corpses were disposed of using crematoria in the Japanese biological warfare laboratories. As a result of experiments, field tests, and attacks with biological weapons during World War II, the Japanese killed a total of 580,000 Chinese—slightly more than three-fourths by entomological weapons.

Figure 9.4. A rare photo documenting the work of Unit 731. Although no higher-quality version of the image exists, the photo is sufficient to show a doctor standing in front of a pile of bodies of Chinese prisoners who had been used as human guinea pigs. Corpses were disposed of using crematoria in the Japanese biological warfare laboratories. As a result of experiments, field tests, and attacks with biological weapons during World War II, the Japanese killed a total of 580,000 Chinese—slightly more than three-fourths by entomological weapons.

of Unit 731's work was so thinly veiled in scientific journals as to constitute a veritable confession. Consider Ishii's publication on epidemic hemorrhagic fever in the Japan Journal of Pathology}6 The methods section of the paper described how infected ticks (suborder Ixodida) were macerated in a saline solution, the mixture was injected into monkeys, and the consequent symptoms were monitored. In violation of scientific standards, Ishii did not name the species of "monkey" used in this research, which should have been a tip-off that something was amiss. Furthermore, the body temperatures of the experimental animals reached 104.4°F, and even the sickest monkey never attains such a high fever. Only one primate could register such a temperature—a very ill human. In all, Unit 731 scientists published or presented more than 100 papers, eventually becoming so bold and crass as to refer to the experimental subjects as "Manchurian monkeys" (there are, in fact, no such creatures).

Ishii's demented playground soon grew too large for the walls of his fortress. Although the hub of his empire remained in Pingfan, Unit 731's spokes stretched across Asia.17 The biological warfare network grew to include at least 10,000—by some accounts more than 20,000—physicians, nurses, microbiologists, entomologists, plant pathologists, veterinarians, and other scientists. Some two dozen satellite facilities—some disguised as Red Cross units— formed the support structure for Unit 731.

Lying 70 miles north of Pingfan, just two hours by train, Anda Station served as Unit 731's proving ground. A typical experiment conducted at this remote airstrip was described by Kurushima Yuji, a medical orderly. A square-mile grid of 1,000 boxes lined with sticky paper was laid out, after which an airplane dropped a bomb, which exploded about 300 feet above the grid and rained uninfected fleas over the site. The range and pattern of falling insects provided data needed to set the operational parameters of Uji bombs. However, to fully endorse the device for military use required testing with infected fleas and human targets. According to General Kawashima:

In the summer of 1941, experiments were performed at Anda Station on the use of the Ishii porcelain bomb charged with plague fleas. . . . The persons used for these experiments, fifteen in number, were brought from the detachment's inner prison to the experimental ground and tied to stakes which had been driven into the ground for the purpose. . . . Flags and smoke signals were used to guide the planes and enable them to find the proving ground easily. A special plane took off from Pingfan Station, and when it was over the site it dropped about two dozen bombs, which burst at about 100 or 200 meters [500 feet] from the ground, releasing the plague fleas with which they were charged. The plague fleas were dispersed all over the territory. A long interval was allowed to pass after the bombs had been dropped in order that the fleas might spread and infect the experimentees. These people were then disinfected and taken back by plane to the inner prison at Pingfan Station, where observation was established over them to ascertain whether they had been infected with plague.18

They had. Some died in just two days; others lingered for ten days or more.

In the early 1940s, a combination of drought and wartime destruction led to a famine in China and spawned Detachment 100.19 Fascinated by the scale of death—hunger had killed nearly 3 million Chinese—Ishii advocated exploiting this vulnerability through biological warfare. To develop methods for the destruction of crops and livestock, the Japanese chose a site near Changchun, about 150 miles south of Pingfan.

The historical record is frustratingly silent as to whether insects were developed for crop destruction, although it seems likely that they were considered, given their importance as pests of rice and other Asian crops. For example, the brown planthopper (Nilaparvata lugens) causes "hopper burn" (the rice plants become brown and crisp owing to the insects' feeding) and the green leafhopper (Nephotettix virescens) is a vector of tungro, a devastating viral disease that can wipe out thousands of acres of paddies in a single season. As for vector-borne animal diseases, tick-borne piroplasmosis, a debilitating ailment of horses caused by a single-celled parasite, was investigated by Detachment 100.

Another major biological warfare installation rubbed salt in China's bloody wound. Nanking—a thriving city, resting amid lush forests and stunning mountains in the heart of the country—had been the target of Japan's most brutal conquest. In retribution for having resisted the Imperial Army and served as Chang Kai-shek's capital, Nanking was beaten into submission. During a horrific eight-week period beginning in December 1937, the Japanese turned the city into a scene of depravity: 20,000 women were raped and 200,000 men were slaughtered. A year later, Unit Ei 1644 opened for business.20

Ishii appointed his childhood friend Matsuda Tomosada to head Ei 1644. A staff of 1,500 needed a large facility, and—adding further insult to injury— the unit commandeered a hospital in the heart of the city. In short order, the building was surrounded by the requisite ten-foot brick wall topped with barbed and electric wire and patrolled by guard dogs. To a visitor, the first floor of the converted hospital would have appeared to be a conventional medical laboratory. The second floor, however, would have looked like some sort of diabolic zoo, with cages of mice, rats, and ground squirrels; containers of fleas and lice; and flasks of cholera, typhus, and plague. The third floor was a chamber of horrors. The recollections of a soldier assigned to Ei 1644 provide a terrifying tour:

One had to pass through the main offices in order to get to the third floor, where the cages were. . . . Inside the door, the room was about ten by fifteen meters [30 by 50 feet] with cages all in a row. Most of the maruta [up to 100, but usually 20 to 30] in the cages were just laying down. In the same room were oil cans with mice that had been injected with plague germs, and with fleas feeding on the mice.21

The primary purpose of the Nanking facility was to support the work of Unit 731, with 100 rearing chambers being dedicated to the production of fleas. However Ei 1644 also had a unique program in which lice were mass produced and infected with typhus. There are no records indicating if, when, or where these weaponized creatures were released, so we might presume that they were not terribly effective against the enemy.

The other auxiliary units in support of the Japanese biological warfare effort sprung up in response to opportunity and need.22 For example, Unit 673 in Songo was largely dedicated to the study of the epidemic hemorrhagic fever named after this Manchurian city. Songo (the disease) is caused by a virus that is transmitted to humans by ticks that have fed on infected rodents.

With a network of thousands of researchers and technicians stretched across eastern Asia, the Japanese Army understandably demanded a tangible return on its investment. Jars of body parts, cleverly designed bombs, reams of data, plumes of greasy smoke from incinerators, and small-scale tests were all very fine. But if Japan was to win the war, the real killing would need to begin. Ishii and company were delighted to comply.

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