Canada and Gas Warfare

Poison gas was used throughout the First World War by almost all armies. The various types of gas, delivered by canisters, projectors, or shell, killed, maimed, denied ground and wore down morale. By 1918, soldiers of all armies encountered gas frequently while serving at the front. Canadian soldiers were among the first to face the death clouds, at the Second Battle of Ypres, and they would have a fraught relationship with gas throughout the war. This article will examine the interaction of Canadian armed forces with poison gas, with a focus on its use in attack, the development of a defence doctrine to protect against it, and its impact on individual Canadians. It will also look at how gassed veterans fared in the war’s aftermath and the creation of chemical weapons in Canada during the Second World War.

Poison gas was used throughout the First World War by almost all armies. The various types of gas, delivered by canisters, projectors, or shell, killed, maimed, denied ground and wore down morale. By 1918, soldiers of all armies encountered gas frequently while serving at the front. Canadian soldiers were among the first to face the death clouds, at the Second Battle of Ypres, and they would have a fraught relationship with gas throughout the war. This article will examine the interaction of Canadian armed forces with poison gas, with a focus on its use in attack, the development of a defence doctrine to protect against it, and its impact on individual Canadians. It will also look at how gassed veterans fared in the war’s aftermath and the creation of chemical weapons in Canada during the Second World War.

Stalemate and the Search for Success

The generals expected that the war on the Western Front would be one of marching troops, thrusting cavalry and fast-paced action in a campaign of movement. The first weeks of battle proved that to be the case, with German troops marching through Belgium and sweeping downwards into France as they followed the Schlieffen Plan. But the costs were high. Rapid-firing artillery, modern rifles, and scythe-like machine guns firing hundreds of bullets a minute made any extended advance over open ground by large bodies of men result in devastating losses (see Armaments).

The front stalemated by the end of 1914, with soldiers digging deep to escape the rain of shells and bullets. The ditches became trenches and then expanded into trench systems, eventually running some 700 km from Switzerland to the North Sea. The opposing armies faced off against each other along the Western Front, unsure of how to advance in the storm of steel.

The Canadian Division was lucky to miss these withering battles. Arriving in France in February 1915, it soon set about learning the intricacies of trench warfare. Dozens of Canadians were killed or wounded, usually from sniper fire, as they mucked through shallow trenches. In April, the Canadians were moved to the Ypres front in Belgium, east of the shattered city, in the large salient that jutted into the enemy lines.

By mid-April 1915, the Canadians and other formations in the salient were informed by the British High Command that spies were warning that the Germans were planning to unleash poison gas (see Intelligence and Espionage). No one was certain what this might be, or how it would affect soldiers, and the defensive planning was minimal.

Opposite the British, French and Dominion troops, the Germans were indeed waiting for proper weather conditions to unleash their chlorine gas, in the hope of breaking the deadlock. After several unsuccessful uses of tear gas, German scientists turned to chlorine. Transported to the front in steel canisters and set into the front lines, they were to be released by specially trained soldiers to create a cloud of chlorine that would be blown by strong winds over the enemy lines.

A.Y. Jackson, Gas Attack, Liévin, 1918.

Second Battle of Ypres

On a sunny 22 April 1915, the Germans released their gas cloud, some 6 km long and almost 1 km deep. The uncanny green-yellow tendrils seemed to slither over the battlefield, filling the crevices, craters and trenches, before passing through two French territorial and colonial divisions to the north of the Canadian Division. Choking and gasping in terror, those French troops who did not succumb to the gas as they writhed in agony through corrupted lungs, fled from the front. German troops, no less afraid of the death clouds, advanced tentatively into the gap. 

The Canadians were lucky to escape the worst of the cloud, but those men on the left of the Canadian Division were hacking through burning lungs and firing at the enemy with teary eyes. The Canadians even counterattacked on the 22nd and 23rd, halting the German advance. As they moved forward, they witnessed the French dead and those soon to join them, as they choked on their own fluids, retching up bile and blood. One Canadian survivor wrote: “It is impossible for me to give a real idea of the terror and horror spread among us by this filthy loathsome pestilence.”

The Germans unleashed a second smaller, but denser, cloud on the 24th, directly opposite the Canadians. Some of the Canadian soldiers who had been trained in chemistry had recognized chlorine gas from two days earlier and had instructed men to wet cloths with water or urine to offer minimal protection. As the cloud rolled through the Canadians, soldiers scrambled out of the trenches, firing their Ross rifles when they were not jamming from an overheated breech and faulty ammunition, and escaping from the pooling gas in the low-lying trenches. Those wounded or unable to climb out suffered the worst effects of the chlorine. Under such conditions, the Canadian lines were overrun, although most of the units at the front were able to retreat to a secondary line of trenches, and the German advances were minimal. 

“It is impossible for me to give a real idea of the terror and horror spread among us by this filthy loathsome pestilence. It was not, I think, the fear of death or anything supernatural but the great dread that we could not stand the fearful suffocation sufficiently to be each in our proper places and be able to resist to the uttermost the attack which we felt sure must follow, and so hang on at all costs to the trench that we had been ordered to hold.”
— Major Harold Mathews

Most of the battered Canadians were relieved from the front on the 25th, having suffered over 6,000 casualties. With many of the wounded left behind on the battlefield, it was unclear how many died from gas, but it was likely several hundred. Many more had suffered from ravaged lungs, their war over, although all would face battles to survive in the postwar years and to receive proper pensions. “Imagine Hell in its worst form,” expressed one Canadian sergeant of the chlorine and chaos. 

The poison gas had not led to a breakthrough, but it had clearly been effective on the stalemated battlefront. The Allies scrambled to create effective gas masks for their soldiers, and then to distribute them and train in their use. Several additional cloud attacks were unleashed by the Germans in May 1915 against the British, which killed hundreds and caused terror. But the cloud attacks were difficult to mount, always taking time to haul forward the thousands of gas canisters and waiting for proper wind conditions. The British launched their first cloud attack in September 1915 at the Battle of Loos, only to find that the wind turned and blew large parts of the lethal cloud back on the British troops, disrupting the attack as panic set in. It was a costly failure. Both sides took notice of the unpredictable nature of these clouds that were almost as dangerous to one’s own side as to the enemy.

In 1916, the French and Germans experimented with gas shells during the Battle of Verdun, which lasted almost 10 months. The shells could be directed more accurately to targets but required high concentrations of shellfire to build up the lethal clouds. Deadlier gasses were also developed, with chlorine superseded by phosgene and diphosgene, both of which were more lethal and difficult to identify by smell. Unlike chlorine, which immediately burned the lungs, the nearly invisible phosgene was more insidious, taking time to affect the body. Phosgene and gases like it caused fluid to build up in the lungs. Within hours a victim’s lungs would fill up and gassed men could choke up four pints of liquid an hour, eventually drowning in their own fluids.

Years after the war, one British sergeant recounted that “it is a hateful and terrible sensation to be choked and suffocated and unable to get breath: a casualty from gun fire may be dying from his wounds, but they don’t give him the sensation that his life is being strangled out of him.”

Gas Masks and Respirators

After the first chlorine attack, the senior officers scrambled to find anything that could protect their men against this new chemical agent. The development of a defensive doctrine was haphazard and left soldiers decidedly uneasy as they received contradictory messages and a series of bizarre-looking gas masks. The various respirators became more effective in 1916, with most types having a charcoal filter to remove most of the lethal chemicals. With the introduction of the Small Box Respirator, known as the SBR, in August 1916, British and Canadian casualties were much reduced.

And yet there were always men who were slow to put on respirators or had them blown off their faces by shellfire. Wearing the bug-eyed respirators was also debilitating to morale. Respirators isolated soldiers and forced them to confront their fears alone, away from the sympathetic glance of a mate and only with the soft hiss of one’s own breath in one’s ears. These and other factors all continued to make poison gas an effective weapon that caused casualties and withered morale.

As gas shells were introduced in greater numbers in 1917, it became more common to fire them against enemy gun batteries, forcing the gunners to wear their masks and thereby slow the rate of fire. This type of chemical counter-battery fire was embraced by the Allied gunners, especially Andrew McNaughton, who was the Canadian Corps’s first senior counter-battery officer and rose through the ranks during the war.

With gas so prevalent, there was a need to create specialists to instruct soldiers in protecting themselves from the chemicals. From May 1916, the newly formed gas services recruited men with a firm understanding of chemistry, and these new gas officers instructed throughout the Canadian Corps — which had grown to 100,000 soldiers by early 1917. With only a few dozen gas officers, they would typically lecture to large groups of officers and NCOs from several units about the latest gasses, evolving enemy tactics (such as hiding gas shells within high explosive bombardments or firing at night) and methods for cleaning respirators. These soldiers would then return to their battalions, batteries or companies to further instruct their comrades. Later in the war, there were brigade and battalion officers and NCOs who further specialized in gas instruction.

From the introduction of gas, there was a constant need to instruct, train and update the mass of soldiers. After that, soldiers were forced to march, train and even play games with respirators attached. Photographs of respirator-clad men kicking around a soccer ball were surely one of the signs that the Great War was like no other before it.

Mustard Gas

The gas war changed radically in the summer of 1917 when the Germans introduced mustard gas to the battlefield. Fired in shells marked by yellow crosses — and known initially as Yellow Cross gas — the mustard gas burned lungs like conventional gasses, but also left large blisters on the skin and caused blindness. In the first three weeks after its use, there were over 14,000 gas casualties in the British forces alone. The soldiers had been told that their respirators would protect them, but now the mustard gas burned skin and, even worse, settled into the mud and remained a casualty-causing agent for weeks. With soldiers hunkered down in the muck and slime, every shell crater or trench could now be infected.

The Canadian Corps first faced mustard gas during the Battle for Hill 70 in August 1917, as the Germans harassed the attackers in the lead-up to the offensive on the 15th, and then throughout the bloody affair. The Germans deluged the Canadian artillery with mustard gas on the 17th and 18th, causing hundreds of casualties. In all, 1,122 Canadians were wounded by gas at Hill 70 — almost all from mustard gas. Matters were just as bad at Passchendaele in October and November 1917, as the Canadians suffered through the corrupted gas environment.

Behind the lines, the medical services struggled with this chemical epidemic. Because mustard gas infected uniforms, doctors and nurses were gassed in the late summer as they treated their patients. By the end of the year, men smelling of gas had their uniforms cut off early in the medical process. Oxygen was administered to those with ravaged lungs, but there was never enough to meet the tide of casualties. Those blinded by mustard gas had their eyes washed out, and most had sight return within a few weeks, but severe cases suffered permanent blinding.

Chemical Weapons in 1918

All armies incorporated gas shells into their arsenal by 1918 and it was fired before, during and after battle. Gas may not have led to a strategic breakthrough — but neither did tanks, machine guns and even artillery. Chemical weapons were most effective as part of the all-arms doctrine of the fighting forces, used to achieve different tactical missions, and a key weapon that contributed to the overall strategy of attrition.

By the last year of the war, gas was directed more commonly against enemy gun batteries and the lines of communication. If the horses and mules could be gassed or slowed because they were forced to wear respirators, forthcoming attacks or resilient defences could be disrupted. With horses and mules targeted, their hooves, lower legs and bellies suffered burns and blisters from contaminated mud, many of which became infected and took the animals out of the battle or forced them to be euthanized.

By 1918, chemical shells made up between 20 and 40 per cent of all artillery shells. Gas shells were also used to isolate defenders and set up chemical barriers in order to bypass areas of resistance. The Germans employed these types of chemical shoots during their offensives from March 1918, and Allies did so in their many campaigns from July.

As a shock formation thrown into battle after battle, the Canadian Corps relied heavily on gas for all manner of missions during the Hundred Days campaign, the series of battles from 8 August at Amiens to the end of the war on 11 November 1918. The Corps commander, Sir Arthur Currie, said after the war, “We tried to make his life miserable.… We never forgot that gas at the second battle of Ypres, and we never let him forget it either. We gassed him on every conceivable occasion, and if we could have killed the whole German army by gas we would gladly have done so.”

The Canadian soldiers faced gas nearly every day in the battles of the Hundred Days. The Germans would fire concentrations in the hope of killing or injuring, but also lighter saturations that would force soldiers to don their respirators. The strain of moving forward under fire was exponentially increased by doing it nearly blind, alone and gasping for breath; and the terror of defending trenches beneath a storm of steel and chemicals was unimaginable.

Alexander McClintock, an American who served with the 87th Canadian Infantry Battalion, wrote, “The one thing of which we constantly lived in fear was a gas attack. I used to awaken in the middle of the night, in a cold sweat, dreaming that I heard the clatter and whistle-blowing all along the line which meant that the gas was coming.”

The war on the Western Front ended on 11 November 1918 with soldiers suffering through the gas and fire. The Hundred Days had delivered a surprising if hard-fought victory, and the high command on both sides had planned for the war to go into 1919. If it had, the Allies were set to unleash dense clouds of lethal gas that were thought to overpower the German respirators, which were increasingly fragile with the shortages of key materials from the Allied blockade. Fritz Haber, a leading German scientist, felt that “if the war had gone on until 1919 [the Allies] would have won by gas alone.”

Canadians testing their gas masks after heavy work in the trenches. September, 1917.


It is thought that gas caused one million or more casualties to soldiers in all the armies during the First World War, although it had a low rate of lethality, so most men survived. In Canada, after the war, the Army Historical Section calculated the wartime Canadian gas casualties as 11,572. These were soldiers who had made it to a doctor to have the injury marked in their personnel files. Thousands of additional Canadians were gassed and uncounted, toughing it out at the front or dying in the trenches or no man’s land.

After the war, veterans suffering from the permanent effects of gas had a difficult time appealing for a pension from the government. The authorities in Ottawa checked the personnel files and medical records of soldiers and often they did not mention gas. Even with gas recorded, sometimes men were turned down as authorities claimed their ailments were due to tuberculosis or other diseases not attributed to the fighting. Those who had fought so hard on the Western Front through the clouds of chemical agents often faced long and frustrating bureaucratic battles to have their war wounds acknowledged.

Chemical Agents since the Great War

Chemical weapons on the Great War battlefields were unique in the history of warfare. While gas was employed in other wars, most notably by the Italians against the Abyssinians (Ethiopians) in 1935–36, during the Iran-Iraq War of the 1980s, and more recently by the Syrian regime against its own people in the 21st century, it was never unleashed with such intensity or concentration as on the Western Front of the First World War. During the Vietnam War, the United States used tear gas, as well as chemical herbicides napalm and Agent Orange, which had devastating long-term environmental and health effects.

It was anticipated that gas would be used in the Second World War as a weapon on the battlefield. In the 1930s, there was widespread fear in Britain that enemy bombers would be carrying gas bombs to suffocate those in the cities and tens of millions of respirators were handed out, even special ones for babies. The fear did not lessen from the start of the war, with soldiers and civilians issued respirators, gas capes and special creams.

Chemical agents were not used because of the uncertainty of what the enemy held in store and the challenge of delivering chemical agents on the battlefield. For example, unknown to the Allies, the Germans had developed nerve gas in the 1930s, a far more lethal chemical agent than what the Allies had, but it was not easy to deliver or disperse. The Germans, however, thought the Allies might also have lethal gas. And yet if the Germans had successfully invaded Britain in late 1940 after the fall of France, the British planned to unleash chemical agents to saturate the beach landing zones to slow and injure the Germans. Moreover, late in the war, Churchill had to be talked out of using aerially dispersed gas against German cities, and Hitler threatened to use gas several times during the conflict. Chemical agents were used in concentrated form against the defenceless Jews and other civilians marked for annihilation in the death camps (see Canada and the Holocaust).

While Canada produced no chemical agents during the Great War, laboratories went to work in the Second World War. The Suffield Experimental Station in Alberta was funded equally by the British and Canadian armies from 1941 to 1946. By the end of the war, its nearly 600 staff were involved in making and testing both chemical and biological weapons (see Defence Research).

Between 1941 and 1970, chemical weapons were tested on approximately 2,000 to 3,000 Canadian soldiers, with effects ranging from minor mustard-gas-induced burns on skin to permanent lung damage. It was not until 1988 that the federal government admitted to using soldiers for testing chemical agents, which continued until at least 1970, and only in 2004 did veterans receive financial compensation for their injuries.

Significance and Legacy

Canada has had a long history of using, fighting against, and even manufacturing, chemical weapons. In the second half of the 20th century, Canadian officials worked on the global stage to ban chemical weapons. That they were little used in the many wars of the 20th century, seemed to suggest they might effectively be banned, but several nations have stocks of chemical weapons and they remain a spectre over the many battlefields in the world.

New German gas mask taken by Canadians in Lens. There is no protection to eyes, just a mouthpiece. September, 1917.

Collection: First World War