1000 BC. Arsenic smoke was used by the Chinese.
600 BC. During a siege of the city, Solon of Athens poisoned the drinking water of Kirrha.
184 BC: In a sea battle, Hannibal of Carthage hurled clay pots full of vipers onto the decks of enemy ships.
Dating back to at least the 1100s, there are many examples of hurling the bodies of plague or smallpox victims over city walls.
1400s: Leonardo da Vinci proposed an arsenic-based anti-ship weapon.
1495: The Spanish offered wine spiked with the blood of leprosy patients to the French near Naples.
1650: Polish artillery general Siemenowics fired spheres filled with the saliva of rabid dogs at his enemies.
In 1763, British officers came up with a plan to distribute smallpox-infected blankets to Native Americans at Fort Pitt, Pennsylvania.
During the Civil War, future Kentucky governor Luke Blackburn, MD, sold Union troops clothing contaminated with smallpox and yellow fever.
Near the end of the Civil War, Grant's army was stalled outside Richmond during the siege of Petersburg, Virginia. There was a plan -- not acted upon -- to attack the Confederate trenches with a cloud of hydrochloric and sulfuric acids.
In world war 1 1 million of the 26 million casualties suffered by both sides were from chemical agents.
In 1935, Fascist Italy invaded Ethiopia. Ignoring the Geneva Protocol, which it signed seven years earlier, Italy used chemical weapons with devastating effect. Most effective was mustard gas dropped in bombs or sprayed from airplanes. Also effective was the mustard agent in powdered form, which was spread on the ground.
The Japanese invasion of China featured both chemical and biological attacks. The Japanese reportedly attacked Chinese troops with mustard gas and another blistering agent called Lewisite (named for its U.S. inventor, Captain W. Lee Lewis, who called it "the stuff beside which mustard gas becomes a sissy's scent"). In attacking the Chinese, Japan also spread cholera, dysentery, typhoid, plague, and anthrax.
Germany used a cyanide-based gas to massacre Jewish civilians in concentration camps.
In 1945, 2 atomic bombs were dropped by the United States on Nagasaki and Hiroshima, Japan killing tens of thousands. The fallout killed scores times that more.
In 1967, the International Red Cross said mustard gas and possibly nerve agents were used by the Egyptians against civilians in the Yemen civil war.
Nov 1980, Iraq gases Iran during the war between the 2 countries. Iraq uses Mustard Gas and Tabun. UN investigative teams verify the use of the gas.
Aug 25th 1988, Iraq uses mustard, cyanide, and nerve agents against Kurdish civilians killing 5,000 in Halabja, Iraq.
Heres a few. some I didnt have dates for so I didnt include them. Iraqis after the Gulf War were complaining of depleted Uranium rounds causing birth defects and causing deaths. The soldiers who witnessed the explosions being tested during the manhattan project, and some others from other countries.