In the history of human warfare, "biological weapons" has always been an unavoidable topic, as early as the fourteenth century, the Tatars had used this "special weapon" when attacking the city of Faka because they were hindered, they used catapults to throw the bodies of people who died of plague into the city of Faka, causing the plague to spread in the city, and finally used this cruel method to break through the city of Faka, which was the earliest case of the use of biological and chemical weapons in the history of war, and in the period of World War I, The Germans also used poison gas for the first time on a large scale in the Battle of Ypres in Belgium, when this one-man-high yellow-green smoke cloud was blown by the breeze of 2-3 meters per second to the British and French positions, due to the lack of knowledge of poison gas, the British and French defenders suddenly fell into chaos, the front quickly collapsed, and the German army behind the smoke cloud broke through the British and French defenses in one fell swoop without encountering any resistance.
After the end of the First World War, the remarkable results of the poison gas attacks attracted great attention from the international community, and although the Geneva Conventions adopted the Protocol prohibiting the use of asphyxiating, poisonous or other gases and bacteriological methods of warfare in war, they did not strongly restrict the development and use of such weapons, and chemical weapons became a prohibited weapon of mass destruction. In 1929, in preparation for a war of foreign aggression, Japan began to build chemical weapons production facilities on Ōkuno Island, and this "poison gas factory" is little known even in Japan due to its extreme secrecy to the outside world. After the outbreak of the July 7 Incident, the First Field Chemical Experiment Department of the Japanese Army invading China issued a report to the base camp, the general content of which was: The Chinese army is not only not equipped with anti-poison suits and fire powder, but also has no ability to protect against erosive agents, and they can hardly see any facilities that can protect poison gas when fighting on the battlefield.
After receiving the report, the top brass of the Japanese army began to "throw" international law aside, and instead listed weapons of mass destruction such as "poison gas" as "ordinary weapons of war", because they knew in their hearts that in the face of the Chinese army with backward equipment but brave combat, poison gas was the "most ideal" weapon. At the beginning of the war, due to the fear of being condemned by the international community, the Japanese army only dared to sneakily use "biological and chemical weapons", but after 1938, as the war in China gradually fell into a stalemate, the number and scale of the use of chemical poison gas by the Japanese army eager to win began to increase greatly, and only when attacking Jiangxi Xiushui, the Japanese 11th and 16th Divisions concentrated more than 140 cannons to fire more than 3,000 poison gas bombs and 15,000 poison gas cylinders at the positions of the Chinese defenders. The nationalist positions on the opposite bank were completely covered by poisonous gas in an instant, and most of the officers and men of the defenders were also martyred.
In addition to the use of poison gas when the attack was blocked, the encircled Japanese army would also be used frequently when the dog jumped the wall, in the Yichang counter-offensive, the Chinese army became more and more courageous, the 13th Division defending Yichang was fully surrounded, at a critical juncture, the Japanese commander Uchiyama Hidetaro even began to burn secret documents and flags, ready for suicide, and it was at this time that Endo Saburo's aviation troops suddenly flew to the battlefield and began to suppress Chen Cheng's attack in the air, in addition, the 13th Division also came up with the final The "killer weapon" - poison gas bomb, the result instantly changed the situation on the battlefield, forcing the Nationalist army to stop attacking. In the entire war of aggression against China, the reason why the Japanese army was always able to "hit where they wanted to go" and win one battle after another was that in addition to the powerful troops, the "biological and chemical weapons" also occupied a great advantage, but since this weapon was so easy to use, then after the outbreak of the Pacific War, in the face of the United States, whose comprehensive national strength was stronger than its own, why did the Japanese not use this "cheap" weapon of mass destruction?
In fact, long before the outbreak of the Pacific War, the United States had been closely concerned and strongly condemned the use of poison gas by the Japanese army on chinese soil, and in 1941 it issued a public statement saying: If Japan continued to use this inhumane weapon of war, then the United States would regard this behavior as an action against itself and give the same and full retaliation. Later, with the outbreak of the Pacific War, the Japanese army's "biological and chemical weapons" have become a real threat to the United States, so for the protection of this aspect, the Americans have been fully prepared, and on the other hand, the Japanese side, in fact, they are also very clear in their hearts, the Americans absolutely have enough to make them fearful and more advanced biochemical technology, if they take the lead in using this weapon, then the United States is bound to launch more crazy retaliation. And perhaps it was this self-knowledge that prompted Hideki Tojo to finally order a complete end to the use of such "weapons of mass destruction."
After the order was issued, even if the Japanese army in the Pacific Theater was completely annihilated, it would never use "biological and chemical weapons" against the US military first, but the Japanese army on the Chinese battlefield was not so "obedient", they would still use such weapons secretly, and the ultimate reason was - bully you did not!