Before and during the Sino-Japanese war, the Japanese Imperial Forces had produced various Chemical Weapons. Among the CW agents produced were phosgene, mustard, lewisite, hydrogen cyanide, and diphenyl cyanarsine. During the war, they were carried into China and some of them were used against Chinese military forces and civilians. The Japanese chemical weapons inventory consisted of various chemical-filled munitions, including artillery shells, aerial bombs, grenades, and mortars. Most Japanese weapons were developed during World War II.
Some chemical field munitions were left behind in the Aleutian Islands after Japanese World War II occupation. These weapons may have been left with booby traps in caves on Attu and Kiska Islands. When Japan was defeated in 1945, the Imperial Japanese Army stationed in China had abandoned their chemical weapons, which were dumped into rivers or buried. Most of the Abandoned Chemical Weapons [ACW] in China, estimated at about 700,000, are buried in the Haerbaling District of the City of Dunhua, Jilin Province. There may be another two million chemical munitions, including the 1.8 million rounds suggested in the historical records, abandoned in the Dunhua region of Jilin Province. The burial sites and the temporary storehouses are widely scattered from Zhejiang Province in the south to Heilongjiang Province in the north. Most of the unearthed ACWs are found corroded and damaged due to a long period of burial since the end of the war.
Since 1990, the Chinese government has urged the Japanese government to dispose CW which Japan had left in her territory. The Government of Japan has been making efforts to solve the issue of chemical weapons abandoned in China by setting up the Abandoned Chemical Weapons Coordination Council in August 1997, following approval of the Cabinet. As part of the effort, the Technology Study Group for the Destruction of Abandoned Chemical Weapons (hereafter called the Study Group) was established. Its task was to study various technologies for destruction of the ACW from technological and professional viewpoints, and to present its view to the Coordination Council.