Also from WW2 after WW2
The situation in the Far East in 1945 was quite different. Japan’s chemical stockpile was smaller and less sophisticated than Germany’s; on the other hand, (along with Italy) Japan was one of two nations to use chemical weapons during WWII and by far and away the most prolific user. Japanese use of chemical weapons against China is well-documented (including actual photographic evidence during the occupation of Shanghai) and estimated to have cost China 10,000 casualties. Japan’s chemical warfare program was largely outside of the home islands, and centered at Unit 516 at Cicigar in the puppet nation of Manchukuo (today Qiqihar, China). Unit 516 was subordinate to Unit 731, the overall imperial special weapons outfit more famous for it’s gruesome biological warfare experiments.
The above drawing of a Japanese chemical bomb was prepared by the US Navy in 1945. The types of chemical weapons were lewisite (L in the modern US Army code), mustard gas (HD), phosgene (CG), and cyanide (AC) along with (actually, most commonly) an agent the imperial army called “yellow gas”, a cocktail of HD and L. Over 2 million bombs and artillery shells were manufactured.
On 9 August 1945, the same day as the Nagasaki atomic mission, the USSR invaded Japan’s puppet state of Manchukuo and northern Korea. Some of the Japanese chemical stockpile was captured intact. Opposite their policy in Europe, the Soviets did not retain or study the Japanese chemical weapons. Initially, Stalin refused to transfer any to Mao’s communists and ordered it all destroyed. However years later, as the red army completed it’s pullout from Manchuria, some Soviet-made chemical weapons were transferred to Mao’s troops. During the 1980s the PRC army’s chemical weapons stockpile included modern Chinese manufacture, alongside aging WWII-era Soviet and Japanese ordnance, so either some was inadvertently transferred, or, the Chinese themselves recovered and refurbished some.
After the Emperor’s 15 August 1945 surrender announcement, orders were issued to forces on the Asian mainland to destroy in situ any and all chemical weapons in their possession. Some units in Manchukuo possessing chemical rounds were already in motion due to the Soviet attack. None were properly destroyed, many were thrown into Manchuria’s Nen river, others were buried wherever the possessing unit happened to be at the time. This led to a scattershot effect as small quantities (sometimes one or two individual shells) was buried along the side of a road, in a culvert, or wherever. By intent, none of the locations were marked.
When China’s building boom started in the 1980s this increasingly caused problems as workers in formerly rural areas struck long-buried chemical weapons. Due to the haphazard way Japan’s chemical warfare effort ended, these ranged in quantity from lone individual mortar rounds, up to (for example) a find in April 2001 of 193 artillery shells and four 55 gallon drums in one location.
Between 1999-2005, a total of 281 WWII Japanese chemical weapon items (artillery shells and bombs) were recovered in China at Japanese expense, in addition to those China itself had been storing, in some cases since the 1950s. By the end of 2013 about 50,000 items had been destroyed. In January 2017 another 2,500 items were destroyed. The estimate of what remains unaccounted for in 2017 is an item of dispute; Japan feels between 200,000 to 300,000 items while China has quoted figures as high as half a million.
