The world is officially 'free' of chemical weapons. Here's what that means

The U.S. once had more than 30,000 tons of chemical weapons, but it has finally eliminated the last of its stockpile. (David Zalubowski/AP)

The United States has officially destroyed its stockpile of chemical weapons.

In doing so, it is the last of eight countries to destroy its declared stocks of chemical weapons under the Chemical Weapons Convention – an international treaty signed by nearly 200 nations that bans the possession, production and use of the weapons on the battlefield.