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. [Read more] – Michael’s Blog