occurred in 1942, this germ weapon attack consisted of airdropping ceramic bombs over the city. The aftermath of the attack and the war Japan surrendered to American Allies on September 2, 1945. The United States planned to prosecute Japanese war criminals in both “major tribunals and minor trials”, as stated by General Douglas MacArthur. Very little was known about Japan's biological weapons until 1944, when breakthroughs in decoding Japanese communications had been made by American intelligence. However, those who led Unit 731 were not put on trial; though information had surfaced on the Japanese biological weapons program, it was not connected to Unit 731. This was potentially an official cover-up, attributed to the perceived military value seen by the USA in the information that Unit 731 held, such as the effects of biological agents on humans. The USA itself had researched biological and chemical weapons, specifically through the US Army Chemical Corps. The failure to prosecute those involved in biological warfare may also have been due to lack of due diligence in the investigative process. It has been speculated that the USA helped with the cover-up of a factory in Okunoshima that produced mustard gas and phosphene gas. During this coverup, thousands of tons of poison gases were allegedly dumped into the ocean in 1946. General Shirō Ishii provided the Americans with documents revealing secrets of the Japanese warfare program. General Ishii was not prosecuted for his activities. The Soviet Union captured some Unit 731 personnel whilst they were fleeing from Manchukuo. Some of these captured men stood trial in the Khabarovsk War Crime Trials held between 25-31 of December 1949 in the Soviet Union. During these trials, twelve Japanese medical army researchers were convicted of war crimes. Japanese Major General Yoshiyuki Kawashima testified that Unit 731 had dropped plague-contaminated fleas on Chinese cities that had caused epidemic plague outbreaks. However, these trials were labelled as propaganda by the United States. It has been said that the trials do not offer enough independent verification on the subject and certain crucial points. Many of the leaders in Japan's secret biological warfare program went on to have successful careers in the USA. Many of the activities undertaken by the Japanese army are omitted from historical textbooks and Western culture. Historiography Compared to other histories, the topic of the Japanese biological weapons program is relatively understudied. This is due to the lack of