Last week, a young Lieutenant named Ernst Jünger had his first taste of battle near the ‘Valley of Death‘ above the Woëvre Valley. Describing the gruesome charnel-house of corpses, craters, and shrapnel-stripped trees in his memoir Storm of Steel, Jünger remarks on the constant birdsong and clicking and scuttling that reigned so incongruously between the roaring of guns. The Western Front is not entirely lifeless: the trenches themselves are filled with rats and lice, and of course there are always the buzzing flies, and even cattle grazing behind the lines. As if to defy the man-made deadlock, green shoots and bright blossoms insist on pushing back against the metallic rain and hurricane-force overpressures of massed artillery shelling. Life endures. Spring blooms.

In Flanders, where the Belgian Army’s portion of the Western Front ends at the top of the Ypres Salient, trench warfare has assumed most of the hellish routines by which we remember it. One of these is artillery fire before an attack, so the late afternoon bombardment today puts French Army units adjacent to the Belgian line on edge. As the pummeling stops, men of the 87th Territorial Division and the 45th Algerian Division cautiously resume watching for gray figures to appear on their horizon. On their right flank, the 1st Canadian Division also braces for impact.

But instead of Germans with bayonets and grenades and flamethrowers, the colonial troops see a green cloud blowing across the ground, ignoring the barbed wire defenses and mud that would slow any human wave to a crawl. Sprayed from canisters as seen above, it is chlorine gas, an abundant byproduct of Germany’s advanced immense chemical industry. As an attempt to solve the problem of intractable trench warfare via technology, it is the purest expression yet of the scientific and industrial approach to war. It is also swift as the wind and silent like the grave.

As an inkling of the ecocide which begins today, France and Belgium will remove almost 1,500 square miles (375,000 hectares) of barbed wire during postwar reclamation. Given the widespread and repeated application of chemical weapons by both sides over the next four years, it is not unreasonable to assume that a much larger area is exposed to chemical weapons in the course of the conflict. With molecules heavier than air, the hundreds of thousands of tons of chlorine gas used in the course of the war settle on the lowest ground, scour all life from the dirt, and condense as a dusty film of death on the land.

Poisonous gas thus joins the high explosives and other munitions that are already leaving an enduring legacy of contamination and intentional destruction of nature as well as human life. Some of the best-preserved trenches along the Western Front today are also the most toxic; a century on, metal and chemical levels remain too high in much of the ‘Red Zone’ for any kind of pastoral or agricultural use. Postwar chemical munitions dumping still renders many areas off-limits to the public. Belgian and French bomb disposal teams deal with hundreds of Great War munitions every year; some of them are unexploded chemical shells.

Having fewer chemical factories than Germany, France also lacks the wherewithal to respond in kind immediately. This ‘chlorine gap’ will only spur French scientists to invent even more deadly alternatives, such as phosgene and mustard gas, in parallel development with Germany. Britain, which has enough chlorine to respond quickly, will mount their own first gas attack in less than five months — roughly the same amount of time that Fritz Haber spent preparing for today’s operation.

Yet gas does not solve the problem of entrenched defenders, for the everyday soldier is an infinitely adaptable creature. Chemical defense evolves very quickly as men cover their faces with handkerchiefs and rags, often soaking them in urine. Although more than 1,100 men drown from the hydrochloric acid formed in their lungs, and many more are injured, others abandon their low-lying trenches to escape the worst effects.

Nor does chlorine produce the hoped-for breakthrough. Caught at the edge of the attack, the Canadians call for reinforcements and extend their flank to cover the lost front as soon as the cloud has passed. Despite their breathing masks, the German troops wait for the same cue before moving to the attack, and then they still must pick their way through the wire and mire. By the time the attack has fully formed, an improvised defense is also falling into place. As a result, the gas attack leaves an impression of success — 150 tons of chlorine has killed more than a thousand men — without delivering an actual success, for the allied defense buckles but does not break.

Despite this failure, the face of battle will now change forever. Those magnificent mustaches still adorning so many lips in 1915 are utterly impractical in a chemical environment, for they make it hard to seal a mask to one’s face. Fancy headgear and feathered foppery may look impressive, but they are burdensome extravagances when you are trying to don a gas mask. As the chemical weapons become more deadly, so does the urgency of protection. Yet these are just material problems, easily understood in a series of production statistics on razor-blades and hats; it is less commonly understood that the survival pressures of the chemical warfare environment also put extraordinary stress on the human mind.

The claustrophobia of being enclosed and sealed from the world in order to survive it is as warping on a human soul as the constant shellfire of a watch on the front line; it is not altogether dissimilar from astronaut psychology on a spacewalk. Those of us who have endured the rigorous defensive training of modern armies understand what it is like for the loudest sound in the world to be one’s own breath, to be unable to scratch one’s nose, to broil in protective gear under a hot sun, unable to piss or drink or smoke, for what seems like an eternity. Now imagine fighting in such a condition, for even aiming a rifle while dressed this way is a different, and more difficult, task.

As it leaves a permanent scar on the natural world, chemical warfare also endures in psychological and cultural features of modernity. Gas masks signal horror, apocalypse, and suffering — as is entirely appropriate. We call them ‘weapons of mass destruction’ for good reason.