More from Elyse on the history of chemical warfare.
Chemical weapons created so much misery in World War I that in 1925, the world's leading nations signed the Geneva Protocol.
Their pledge: to never again use gas or bacteriological methods of warfare.
Since then, however, many signatories of the Geneva Protocol have ignored the treaty.
These include Japan, who relied on mustard gas during its occupation of China in the 1930s and 1940s, and fascist Italy, who resorted to chemical agents during its 1936 invasion of Ethiopia.
The most extreme violation, however, was by Iraq, during the Iran-Iraq war.
Between 1980 and 1988, about 100,000 Iranian soldiers died from mustard and nerve gas attacks.
That CIA estimate does not include the civilian population contaminated in bordering towns.
Many of these people developed blood, lung and skin complications long after the war ended in stalemate.
By returning the issue of chemical weapons to the headlines, Iraq helped spur a newer, comprehensive effort to abolish chemical weapons.
In 1996 the U.S. -- who helped develop chemical weapons, but have never used them -- was one of the signers of The Chemical Weapons Convention, which outlawed the use of all deadly chemical agents.
But as history shows us, when a nation is resolved win a battle at any cost necessary, no weapon of war is considered taboo.