Could someone explain this to me? Im German after all!
During the Great War, chemical weapons were used to break the stalemate of trench warfare. The first successful large-scale attack with a lethal agent was used by Germany during the battle of Ypres against the French, I believe, they used Chlorine gas to choke them and burn lung tissue.
Fast forward to late in the war, Germany had developed Mustard gas which is a blistering agent that causes horrific burns when it comes into contact with the skin, eyes, nose, and throat. It's effects were horrific and it blinded a lot of troops that were on the receiving end.
During the later stages of the war, the U.S. deployed trench raiders armed with the Winchester 1897 trench model shotgun. It's effects were absolutely devastating in close-combat and Germany actually filed a formal complaint against the U.S. for using shotguns in warfare as they were deemed "excessive" due to their close range lethality. They threatened to execute any U.S. troops caught with shotguns or shotgun shells, but there is not evidence of this every happening.
For a more theatrical and dramatized version of what trench raiding with an 1897 Trench gun looked like, I'll leave it to my good buddy Garand Thumb....