“Yellow Rain” Biological Warfare Agent Use
Evidence and Remaining Questions
Reports in the late 1970s of alleged chemical and biological weapons (CBW) attacks in Southeast Asia and Afghanistan, collectively known as “Yellow Rain,” sparked the first large-scale investigation conducted by the United States into allegations of CBW use. The official U.S. conclusion was that biological toxin weapons had been used in Southeast Asia and Afghanistan. However, these conclusions were met with skepticism by some and alternative explanations (as outlined in Chapter 4 in this volume by Meselson and Robinson). Based in part on underlying evidence released in December 2003, recent analysis of evidence from the Yellow Rain investigation supports the claim that CBW attacks occurred, yet questions still remain as to identification of the agent, characterization of the incident, and attribution of the attacks to a specific perpetrator.1
This chapter outlines the history behind the allegations of CBW use, details the U.S. government’s investigation, and reviews the subsequent challenges to the U.S. conclusions. It presents findings derived from recently released evidence that clarify some of the debated issues.
The Yellow Rain investigation serves as an important case study for examining the challenges of proving or disproving use and assigning attribution in a CBW investigation. The ability to assess an allegation accurately has implications for monitoring compliance with international legal agreements, and also