Chemical and biological warfare has a long history in East Asia. One of the world's major documented uses of CW (and BW) agents was by Japan in China just before and in the early stages of WWII. Later, Vietnam saw the use of riot control agents (RCAs) and herbicides on a vast scale by the United States during the war, and the Vietnamese probably used some RCAs in return. Finally, the United States accused the Soviet Union and various East Asian client states of using a toxin, popularly referred to as "yellow rain," in the years after the US departure. None of these events is within the scope of this book, although discussion of the Vietnam War and the yellow rain reports is necessary for the analysis of other allegations.
Within the purview of this study, at least ten states in East Asia have been accused of some level of offensive CW activity. There are substantial cases against only four of those countries -- Vietnam, both Koreas, and the People's Republic of China. These countries are given complete reviews. The others are either marginally suspected of minimal activity or, alternatively, strongly accused without much publicly available supporting information. Thus, while the past chemical wars and the possible present stocks are worrisome, the rumors are more so; both make East Asia fertile ground for future proliferation.