by Evan Thompson
As the year 1944 turned to the year 1945, the Japanese war effort against the United States of America continued to face setback after setback. By the end of the war and during the occupation, many Japanese who were involved in World War 2 were taken into custody. As such, the United States conducted interrogations of Japanese prisoners to confirm its suspicions of Japanese biological weapons research. Many different prisoners from different walks of life, who held various positions, gave the Americans varying answers about their role in the Japanese military. While most of these POWs gave reliable information regarding the inner workings and processes of the Japanese military, one commonality was a lack of knowledge about Japanese biological weapons research.
This withholding of information regarding secret biological weapons research was done intentionally by the Japanese government and Ishii Shiro, who kept many top generals in the dark about what was happening to conceal the actual actions being conducted at Unit 731 and other research laboratories. As a result, much of what Japanese POWs knew about Japanese biological weapons experimentation came from rumors or hearsay, according to the POWs. The extent of POW knowledge on biological warfare experiments was that Japan maintained a defensive strategy for using these weapons and would only pursue research for defensive purposes in case of an attack. A 2nd Lt. captured on the island of Biak in Indonesia even went so far as to claim that Japan would never use biological weapons in warfare and that even if they did, it would only be used in a defensive manner. This begs the question of whether or not these captives were lying about their lack of knowledge in order to protect their superiors.
A transcript from an interrogation conducted on the captured Lt. Col. Seiichi Niizuma reveals that Niizuma had extensive responsibilities, ranging from technological research for the Japanese Army to management of clothing and medical supplies. However, despite his vast knowledge regarding the policies of the Japanese Army, Niizuma claimed no knowledge about biological weapons research upon being questioned about Japan’s capabilities. He explained that the Medical Bureau handled biological weapons experiments, which he was not a part of. Niizuma said that the Medical Bureau was headed by the Surgeon General (the Surgeon General being Ishii Shiro). Still, he said that specific tactical oversight of such an operation may have laid with someone else. 
The fact that someone of Niizuma’s rank did not know who was in charge of tactical oversight in the Medical Bureau suggests that Ishii made sure to keep his position in the Medical Bureau vague and unknown to distance himself from any rumors about Japanese biological experimentation.
In another transcript, a nameless POW (Ranked: Lance Cpl.) who had worked at the Water and Purification Department headquarters in Nanking divulged information about the layout of the HQ and the work being done there. He identified the types of bacteria being cultivated at the Water and Purification Department to be cholera, typhus, and dysentery, with the possibility of yersinia pestis (the plague) being cultivated and experimented with as well, starting in 1944. However, he maintained that these types of bacteria were cultivated for usage in vaccines. The vaccines in question used other raw materials such as eggs, agar-agar, casein, meat extracts, animal blood, glucose, maltose, and animal liver, with the animals being housed in a separate compound. The POW also described runoff from the facility as being a yellowish substance that smelled like rotten fish, which was dumped into the sewer after being cleaned.
A more notable account from the interrogation comes later when the POW also provides information about a part of the building that was highly restricted. Earlier in the interrogation, the POW provided a sketch of the compound in Nanking (the sketch was not included with the interrogation transcript), in which he labeled “Building A” as the building where bacteria was cultivated and “Building B” as the building where animals were housed. According to the POW, the second and above floors in Building A were only accessible to army and warrant officers with special access badges. The POW further explained that it was strictly forbidden for Japanese soldiers and civilian workers of the Water Supply and Purification Department to discuss anything pertaining to anything related to their work. As a result of this strict mandate, many of the workers of different departments did not even know each other. Furthermore, the POW explains that in the event that Japan did launch an attack using biological weapons, only the division commanders in the area of the attack would be notified, while all soldiers and civilians would be kept in the dark.
The testimony given by the aforementioned POW seems to strongly corroborate the historical argument that the reason so many captured POWs - regardless of rank - had little to no knowledge of the Japanese biological weapons program was because of a distinct effort to make sure no information regarding bacteria cultivation and experimentation was leaked. This effort to intentionally keep personnel in the dark can clearly be seen in the rule which forbade soldiers and workers attached to the Water Supply and Purification Department from discussing their work.
Another POW, Lt. Gen Hiroshi Kambayashi, was very opinionated when talking about biological weapons. He was firmly against using biological weapons in his interrogation, explaining that they would cause as much damage to the Japanese population as they would to the enemy population. However, he justified Japan’s biological weapons research by explaining that Japan was forced to study these weapons out of necessity due to fears of an oncoming attack. When asked whether or not Japan was pursuing research to use biological weapons offensively, Kambayashi replied that Japan was only studying the offensive capabilities of biological weapons to understand how to defend against an attack fully, should one occur. He also stated that he believed researching biological weapons would be almost impossible because it would have to remain a secret, which would be very difficult to do during a war. 
By trying to justify Japan’s biological weapons research, Kambayashi revealed some critical pieces of information. He first confirmed that Japan was cultivating, researching, and producing bacteria and other pathogens to be used in biological weapons. Not only did Kambayashi confirm that biological weapons research was being conducted, but he also alluded to the probability that Japan was simultaneously researching offensive strategies for biological weapons, which had confirmed American suspicions.
Kambayashi identified Ishii Shiro as head of the Water Supply and Purification Department, further proving Ishii’s role in researching, experimenting, and producing biological weapons under the pretense of “water purification.” Ishii was known to most Japanese civilians and soldiers as the inventor of an effective water filter, which gave Ishii credibility as the head of the Water Supply and Purification Department. The position of heading the Water Supply and Purification Department also came with a lot of power, which Ishii Shiro could manipulate to conceal the biological weapons experiments he was conducting.
A transcript from the interrogation of a Japanese POW captured in Chungking, China details the instances in which bacterial weapons were used in warfare in Central China by the Japanese Army. According to the POW, the known types of bacteria being cultivated by the Water Supply and Purification Department in Nanking included: typhus, dysentery, and cholera. As stated before, in the interrogation of the Lt. Col. POW, the Nanking facility had a restricted fourth floor, which few officers had access to, and the floor was heavily guarded at all times. According to the POW, the belief was that this floor was responsible for conducting bacteriological warfare in Central China. The POW also confirmed that there were rules in place that prohibited the discussion of bacterial/biological warfare among the ranks of the Japanese Army. This rule was taken very seriously, to the point where a group of soldiers unknowingly advanced into an area still affected by a bacteriological attack faster than anticipated, which caused a considerable amount of soldiers to die.
The POW provided four known instances in which the Japanese Army had used bacteriological weapons. The first three instances were in May 1942, during the Chekiang-Kiangsu Campaign, where the Japanese used bacteriological weapons on three different occasions. The first use of bacteriological weapons was in the Kiangsu Province, where the Japanese Army used typhus in the field. Then, in Shang Hsiao, the Japanese Army again used bacteriological weapons, employing dysentery. The next attack came in the Chekiang Province, where cholera, dysentery, and typhus were all used in a special attack. The last instance of a bacteriological attack perpetrated by the Japanese Army came the next year, in November of 1943, wherein the Changte campaign, near the Hunan Province, cholera was used to attack the area. In every one of these attacks, the bacteria was dropped from an airplane onto the affected area, though the number of bacteria used was unknown. These reports of Japanese bacteriological attacks in China prove the existence of Japanese research on the offensive use of biological weapons.
To read more primary source documents, check out our BETA archive http://pacificatrocitiesedu.reclaim.hosting/items/browse
1. Interrogation Report #539, Box 11 (16), (33), National Archives
2. Seiichi Niizuma & Ryoichi Naito, Box 4 (9), (13), National Archives
3. Kambayashi, Box 4 (15-19), National Archives
4. Kambaysahi, Box 6 (10-13), National Archives
5. POW 230, Box 11 (17), (4-5), National Archives
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