Only the first world war saw significant use of chemical weapons, and those for the most part were relatively benign mustard and tear gases. Artillery fire caused a lot more casualties, but there was something insidious about gas attacks that caused the major powers to agree to ban their use in future conflicts. Nothing was said about the stockpiling of such weapons, however, and both Russia and the U.S. brewed up tons of the stuff in storage as part of their Cold War arms race.

On this day, June 1, in 1990, with the Cold War nearing and end, Russian leader Mikhail Gorbachev visiting President George H. W. Bush in Washington D.C. signed a treaty agreeing to halt production of chemical weapons and to reduce their current armaments by 20%.

The chemical weapons in question greatly more lethal than the WW I-era ones; even storing them was dangerous business. In Russia a small leak at a secret military installation near Sverdlovsk (now Ekaterinburg) that released a large amount of anthrax into the air caused an epidemic affecting thousands. Although the Russians tried to keep the incident secret, the story gained traction as major British and West German newspapers ran stories based on reports from survivors.