Airplanes, Machine Guns, & Poisonous Gas were first used in WW1.
Airplanes: Aircrafts was used all the time during the war, esspecially for artillery spotting.
Machine: Machine guns were designed for people to use in WW1, such as the lewis gun which had a 47 or 97 round pan magazine
Poisonous Gas: Phosgene, Chlorine, & Mustard Gas was used commonly during WW1.
