A recent edition of Dan Carlin's wonderful podcast series Hardcore History recounts a frightening moment in our civilization's history. Just over 99 years ago this week in a corner of Flanders, the second battle of Ypres was underway. As the battles of World War I descended into the trenches, soldiers were still accustomed to an ethic of war in which the cowardly were executed by their own superiors if they abandoned their post or even if they failed to jump over the parapets into "no-man's land."

In early 1915, German legal minds and generals debated the utility and legality of a new tactic and weapon. They found small loopholes in the Hague conventions on the use of chemical weapons. If chemicals weren't attached to shells but just released from barrels, that might be alright, wouldn't it?

On April 22, 1915, a strange yellow-green cloud began advancing toward the line of Moroccan and Algerian troops at Gravenstafel. Soldiers gawked at the strange sight, some remarking that something "funny" was happening. Nearly 10,000 French soldiers were killed as the cloud advanced through their ranks. And killed horribly.

Chlorine gas is slightly denser than air and so it filled the trenches. The gas mingles with any moist tissues in the body. When chlorine gas was used again a week later on another part of the Ypres line, Private William Quinton described well the effect:

One poor devil was tearing at his throat with his hands, I doubt if he knew, or felt, that he had only one hand, and that the other was just a stump where the hand should have been. This stump he worked around his throat as if the hand were still there, and the blood from it was streaming over his bluish-black face and neck.

Like other soldiers at the battle of Ypres, he suffered before death from the uncontrollable urge to tear out his eyes, throat, and lungs from his own body. These soldiers effectively drowned in their own bodily fluids. Many solders ran into live fire to end their pain. Others just ran away from the line in madness.

Sir John French felt the need to defend the Entente forces from charges of ungallant behavior:

I wish particularly to repudiate any idea of attaching the least blame to the French Division for this unfortunate incident. …if any troops in the world had been able to hold their trenches in the face of such a treacherous and altogether unexpected onslaught, the French Division would have stood firm.

The old military norms meant to encourage gallantry and nobility could not withstand the tactics of Operation Disinfection, especially when it was combined with a form of trench warfare that spent tens of thousands of lives without buying an inch of territory.

French's invocation of a "treacherous" onslaught reflected the immediate opinion of chemical warfare among most of the Entente Powers' leaders. It also reflects an ancient and special disgust at weapons that inflict indiscriminate death. This is found in the fear of biblical Assyrians who punished entire cities to get to their king. It is reflected in the attempted medieval prohibition of the crossbow by Pope Innocent II. Both sides in WWI leveraged this same moral revulsion in their propaganda efforts. In recent history, the U.S. has tried to advertise the very discriminating nature of its newer weaponry and tactics, from smart bombs to drones.

The chemical attack and shelling at Ypres and other battles, combined with the seemingly interminable no-stakes-but-our-lives nature of trench warfare, overturned traditional notions of bravery and nobility in war. Military forces and populaces cultivated pity and sympathy for victims of shell-shock, rather than the traditional disgust for so-called cowards and defectives. This form of warfare inspired an almost entirely new kind of war poetry, represented by Wilfred Owen's "Futility" and other verses; war is bleak, meaningless. It inspired resistance to World War II when American "isolationists" railed against a President Roosevelt who would "plow under every fourth American boy."

And it inspires weapons abolitionism today. Diplomatic and moral effort is expended to enforce and spread the norms that Germany broke at Ypres. Humans can never make war entirely rational, but a war that is akin to extinguishing insects is difficult to conduct precisely because it eliminates even the possibility of heroism. One German soldier at Ypres recounted what he had done in horror this way:

What we saw was total death. Nothing was alive. All of the animals had come out of their holes to die. Dead rabbits, moles, rats, and mice were everywhere. The smell of the gas was still in the air. It hung on the few bushes that were left. When we got to the French lines, the trenches were empty. But in a half mile, the bodies of French soldiers were everywhere. It was unbelievable.

All this death was accomplished just by measuring the wind and opening barrels. By treating humans like pests, all notions of nobility, duty, and even mercy are obscured, too. The efforts to eliminate chemical weapons are not just to save lives, or to further tip the balance of world power toward existing conventionally armed powers — they are an effort to save our traditional understanding of military service and valor.