What type of gas was used in World War 1 against soldiers in the trenches?

Answer 1

The first use of gas in World War I was France's employment of grenades containing tear gas against the advancing German army in 1914. The gas, which was more of an irritant than a poison, was used in desperation to stop the seemingly unstoppable German troops.

Later, in October 1914 German troops fired an irritant chemical which caused violent sneezing at British and French troops while attacking Neuve Chapelle. It was intended to incapacitate the Allied troops so they could not defend their positions.

The first use of a poison gas that directly contravened the Hague treaty (which prohibited the launching of projectiles containing asphyxiating or poisonous gas) was by the German army at the Second Battle of Ypres in 1915. The gas used was chlorine which had a devastating effect catching even the German army by surprise; they were unprepared to seize the opportunity to advance which the gas attack provided.

After the 'rules' of war had been broken, with the deliberate employment of a chemical weapon, other nations with the ability to manufacture poison gas could now use it on the battle field. The first Allied nation to use poison gas in response to the Ypres attack was Britain, this time Chlorine again, against the German front at Loos later that year. The plan was to follow up that gassing with an infantry assault but the British front-line was left with 2,000 casualties and several fatalities after the wind changed direction, sending the gas back at them.

The development of poison gas continued throughout the war. The French first used a gas called phosgene which was similar to Chlorine but far more effective; it was responsible for about 85% of the 100,000 chemical weapon fatalities over the course of the war. It was a colourless gas making it difficult to detect and symptoms could take up to 24 hours to show, meaning seemingly healthy troops could fall incapacitated on the front-line.

The most notorious WWI gas is arguably mustard gas. The blistering agent was not intended to kill but to wound the enemy and render them unable to fight. Its use by both the Allied and Central Powers from 1917 until the end of the war would leave the surviving victims of it with devastating, blistering burns, and often blindness.

There were many other gases developed and used during the war but, towards the later stages, as chemical weapon use increased its overall effectiveness diminished.