Poison gas 20 times more lethal to humans than potassium cyanide. It cripples the central nervous system, blocking the action of an enzyme that removes acetylcholine, the chemical that transmits signals. Sarin was developed in Germany during World War II.
Sarin was used 1995 in a terrorist attack on the Tokyo underground by a Japanese sect. It is estimated that the US had a stockpile of 15,000 metric tons of sarin, and more than 1,000 US rockets with sarin warheads were found to be leaking 1995. There are no known safe disposal methods.