Chemical warfare is war fought with chemicals. The development of chemical weapons and defenses against these weapons are usually considered together in military training. These weapons can be designed to kill large numbers of people, disable them for a while, or destroy their food supplies. The weapons are usually effective without destroying property. Chemical agents affect the nervous system, breathing centers, skin, eyes, nose, or throat. They include gases, liquids, sprays, and powders.

They can even be sprayed by airplanes, dropped as bombs, fired by artillery in explosive shells, or scattered by exploding land mines. Some chemical agents, called nerve agents can even cause death. They could be colorless, odorless, and tasteless. They can cause death really fast if a person inhales them or if they are splashed on bare skin. Chemical agents have not been used a lot in warfare since World War I ended in 1918. Other chemical agents do not cause death, but they could make a person unable to fight.

Some of these are called blister agents, which cause big blisters on your skin. A blister agent called mustard gas caused a lot of deaths on both sides during World War I. Some other chemical agents can cause temporary blindness or mental confusion. But people still can defend themselves against all of these chemical agents. For example, gas masks, other protective coverings for the body, and injections of antidotes are used as defenses against chemical agents. Chemical agents also have nonmilitary uses.

For example, riot control agents, including tear gas, can be used to control rioting crowds. These agents just affect the eyes, nose, and throat. They can cause blinding tears and a lot of times, violent coughing. But the effects of the gas aren't too serious because they disappear within a few minutes, or even after a victim gets some fresh air. In the 1950's and 1960's, police and militar forces increased their use of non-lethal riot-control agents to control a lot of internal problems they had.

The same agents were used also in the battlefields of Southeast Asia. The American and South Vietnamese military forces used them in 1965. Another place where a lot of herbicides were used was in the Vietnam War. In this war, the Agent Orange was used to destroy the big-forested areas that were used as guerilla bases..