France, not Germany, was the first country to use gas against enemy troops in WWI. In August 1914, they fired the first tear gas grenades (xylyl bromide) against the Germans.
In January 1915, Germany first used tear gas against Russian armies, but the gas turned to liquid in the cold air. In April 1915, the Germans were the first to use poisonous chlorine gas.
Approximately 30 different poisonous gases were used during WWI. Soldiers were told to hold a urine-soaked cloth over their faces in an emergency.
By 1918, gas masks with filter respirators usually provided effective protection. At the end of the war, many countries signed treaties outlawing chemical weapons.
WWI introduced the widespread use of the machine gun, a weapon Hiram Maxim patented in the U.S. in 1884. The Maxim weighed about 100 pounds and was water cooled.
It could fire about 450-600 rounds per minute. Most machine guns used in WWI were based on the Maxim design.
