In what year were the first chemical agents used, according to historical records?

The first chemical agents were used in warfare during World War I, specifically in the context of hostile military action. Historical records indicate that chemical weapons were first employed in 1915, marking a significant development in warfare tactics as nations began to utilize these new and devastating forms of attack. Prior to this, initial efforts to develop chemical agents had been ongoing, but it was in 1915 that they were first used on the battlefield against enemy troops, creating a long-lasting impact on both military strategy and international law regarding their use. Understanding this context underscores the pivotal moment that year represented in the evolution of modern warfare.