page_title: Chemical warfare
section_title: World War I
hierarchical_section_title: Chemical warfare / History / World War I
caption_attribution_description: English: World War II Gas Identification Posters, ca. 1941-1945
context_page_description: Chemical warfare means using chemical compounds in war to injure or kill people. The chemicals used for chemical warfare are poisonous.
  Chemical warfare has been used since the Stone Age. Since 1899, several international laws have said that using chemical weapons is illegal. But chemical weapons have still been used in wars since then.
context_section_description: Poison gas was first used in World War I. France was the first country to make this type of gas. However, Germany was the first to use it in battle, on March 15th, 1915. On that day, they used tear gas against France.
  The three types of gas used in World War One were:
  Chlorine gas (tear gas): Tear gas makes people cough, have trouble breathing, and go blind until the tear gas wears off
  Phosgene gas: Phosgene caused people to cough and choke much worse than tear gas.  Phosgene gas is a very deadly chemical weapon. Historians think about 100,000 people died in World War I from chemical weapons.  They also think that 85% of these people (85,000 people) were killed by phosgene.
  Mustard gas: Mustard gas was almost impossible to protect against. It caused very bad, painful sores on the outside and inside of the body.
  At first, very basic ways of spreading these gases were used. Even so, many soldiers could be hurt or killed. This was partly because World War I was fought usingtrench warfare, so many soldiers would be in the same place at the same time, and escaping from poisonous gases would be very hard.
  Germany was the first country in World War I to use chemical warfare in battle. They simply opened containers of chlorine upwind of enemy soldiers, so that the wind would carry the chlorine gas to their enemies. 
  Soon after this, the French started using chemical weapons too.  They filled artillery projectiles with phosgene and fired them at the Germans. This was a much more effective way of using chemical weapons. It would become the most common way of delivering chemical weapons during World War I.
caption: U.S. Army poster about mustard gas
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