Anna Feigennbaum at the Atlantic takes us through the century long history of tear gas:
In August 1914, French troops fired tear-gas grenades into German trenches along the border between the two countries. While the exact details of this first tear-gas launch are fuzzy, historians mark the Battle of the Frontiers, as World War I’s first clashes between France and Germany came to be known, as the birthday of what would become modern tear gas.
This early tear gas had resulted from French chemists’ efforts, at the turn of the 20th century, to develop a new method of riot control while maneuvering around international treaty restrictions imposed on “projectiles filled with poison gas” by The Hague Conventions of 1899.
Designed to force people out from behind barricades and trenches, tear gas causes burning of the eyes and skin, tearing, and gagging. As people flee from its effects, they leave their cover and comrades behind. In addition to its physical consequences, tear gas also provokes terror. As Amos Fries, chief of the U.S. Army’s Chemical Warfare Service, put it in 1928, “It is easier for man to maintain morale in the face of bullets than in the presence of invisible gas.”
Today, tear gas is the most commonly used form of what's known in law enforcement jargon as “less-lethal” force. Journalists file news stories of tear gas deployment so regularly that pictures of smoke-filled streets have come to feel like stock photography—a theatrical backdrop of protest. Just this week, police in the St. Louis suburb of Ferguson deployed tear gas to disperse crowds protesting the killing of the unarmed teenager Michael Brown by an officer. Desensitized to these images, people often forget that tear gas is a chemical weapon, designed for physical and psychological torture.
So how did this substance, designed for war, make it from the trenches to the streets?