Poison gas, a new weapon in WWI that changed warfare forever. First developed by the French in August 1914, tear gas grenades were the first biological weapons created to be used in warfare. After being used on the Germans, the Germans launched a serious study to developing these new kinds of weapons. Both sides used forms of gas on each other throughout the war. It first made its appearance at the second battle of Ypres in April 22. The chlorine gas used by the Germans threw soldiers into coughing fits, and burned their eyes and lungs. The Allies retaliated but launched a surprise attack in September 1915. Mustard gas made its appearance at the battle of Riga in September 1917. Mustard gas caused blisters internally and externally and lingered in the soil for weeks. Other gases like phosgane caused choking and coughing and sometimes wouldn’t affect victims up to 48 hours after inhalation. Nerve gas was used at times by the allies and would cause victim’s muscles to tighten too much that they would crush their internal organs. But after 1915 there were fewer deaths from gas because there were ways to protect themselves from it. Poison gas was a major new invention for warfare. It opened a new door for weapons and biological weapons are still used today.